Improve support for themes

[tconbeer]

Follow-up to #80

right now setting a theme just impacts the query editor pane, and it looks bad for most themes:

We could carry the theme colors throughout, with a lot of work.

Unfortunately, these are Pygments themes, which don't line up for Textual's planned support for themes (e.g., light/dark etc.)

[tconbeer]

It actually might not be bad to grab colors from the pygments style:
https://pygments.org/docs/styles/

[tconbeer]

>>> from pygments.styles import get_style_by_name
>>> mo = get_style_by_name('monokai')
>>> mo.background_color
'#272822'
>>> mo.highlight_color
'#49483e'
>>> mo.styles
{Token: '#f8f8f2', Token.Text.Whitespace: '', Token.Error: '#960050 bg:#1e0010', Token.Other: '', Token.Comment: '#75715e', Token.Comment.Multiline: '', Token.Comment.Preproc: '', Token.Comment.Single: '', Token.Comment.Special: '', Token.Keyword: '#66d9ef', Token.Keyword.Constant: '', Token.Keyword.Declaration: '', Token.Keyword.Namespace: '#f92672', Token.Keyword.Pseudo: '', Token.Keyword.Reserved: '', Token.Keyword.Type: '', Token.Operator: '#f92672', Token.Operator.Word: '', Token.Punctuation: '#f8f8f2', Token.Name: '#f8f8f2', Token.Name.Attribute: '#a6e22e', Token.Name.Builtin: '', Token.Name.Builtin.Pseudo: '', Token.Name.Class: '#a6e22e', Token.Name.Constant: '#66d9ef', Token.Name.Decorator: '#a6e22e', Token.Name.Entity: '', Token.Name.Exception: '#a6e22e', Token.Name.Function: '#a6e22e', Token.Name.Property: '', Token.Name.Label: '', Token.Name.Namespace: '', Token.Name.Other: '#a6e22e', Token.Name.Tag: '#f92672', Token.Name.Variable: '', Token.Name.Variable.Class: '', Token.Name.Variable.Global: '', Token.Name.Variable.Instance: '', Token.Literal.Number: '#ae81ff', Token.Literal.Number.Float: '', Token.Literal.Number.Hex: '', Token.Literal.Number.Integer: '', Token.Literal.Number.Integer.Long: '', Token.Literal.Number.Oct: '', Token.Literal: '#ae81ff', Token.Literal.Date: '#e6db74', Token.Literal.String: '#e6db74', Token.Literal.String.Backtick: '', Token.Literal.String.Char: '', Token.Literal.String.Doc: '', Token.Literal.String.Double: '', Token.Literal.String.Escape: '#ae81ff', Token.Literal.String.Heredoc: '', Token.Literal.String.Interpol: '', Token.Literal.String.Other: '', Token.Literal.String.Regex: '', Token.Literal.String.Single: '', Token.Literal.String.Symbol: '', Token.Generic: '', Token.Generic.Deleted: '#f92672', Token.Generic.Emph: 'italic', Token.Generic.Error: '', Token.Generic.Heading: '', Token.Generic.Inserted: '#a6e22e', Token.Generic.Output: '#66d9ef', Token.Generic.Prompt: 'bold #f92672', Token.Generic.Strong: 'bold', Token.Generic.Subheading: '#75715e', Token.Generic.Traceback: '', Token.Text: '', Token.Escape: '', Token.Name.Function.Magic: '', Token.Name.Variable.Magic: '', Token.Literal.String.Affix: '', Token.Literal.String.Delimiter: '', Token.Literal.Number.Bin: '', Token.Punctuation.Marker: '', Token.Comment.Hashbang: '', Token.Comment.PreprocFile: ''}
>>> {k:v for k, v in mo.styles.items() if v}
{Token: '#f8f8f2', Token.Error: '#960050 bg:#1e0010', Token.Comment: '#75715e', Token.Keyword: '#66d9ef', Token.Keyword.Namespace: '#f92672', Token.Operator: '#f92672', Token.Punctuation: '#f8f8f2', Token.Name: '#f8f8f2', Token.Name.Attribute: '#a6e22e', Token.Name.Class: '#a6e22e', Token.Name.Constant: '#66d9ef', Token.Name.Decorator: '#a6e22e', Token.Name.Exception: '#a6e22e', Token.Name.Function: '#a6e22e', Token.Name.Other: '#a6e22e', Token.Name.Tag: '#f92672', Token.Literal.Number: '#ae81ff', Token.Literal: '#ae81ff', Token.Literal.Date: '#e6db74', Token.Literal.String: '#e6db74', Token.Literal.String.Escape: '#ae81ff', Token.Generic.Deleted: '#f92672', Token.Generic.Emph: 'italic', Token.Generic.Inserted: '#a6e22e', Token.Generic.Output: '#66d9ef', Token.Generic.Prompt: 'bold #f92672', Token.Generic.Strong: 'bold', Token.Generic.Subheading: '#75715e'}
>>> gh = get_style_by_name('github-dark')
>>> gh.styles
{Token: '#e6edf3', Token.Error: '#f85149', Token.Keyword: '#ff7b72', Token.Keyword.Constant: '#79c0ff', Token.Keyword.Pseudo: '#79c0ff', Token.Name: '#e6edf3', Token.Name.Class: 'bold #f0883e', Token.Name.Constant: 'bold #79c0ff', Token.Name.Decorator: 'bold #d2a8ff', Token.Name.Entity: '#ffa657', Token.Name.Exception: 'bold #f0883e', Token.Name.Function: 'bold #d2a8ff', Token.Name.Label: 'bold #79c0ff', Token.Name.Namespace: '#ff7b72', Token.Name.Property: '#79c0ff', Token.Name.Tag: '#7ee787', Token.Name.Variable: '#79c0ff', Token.Literal: '#a5d6ff', Token.Literal.Date: '#79c0ff', Token.Literal.String: '#a5d6ff', Token.Literal.String.Affix: '#79c0ff', Token.Literal.String.Delimiter: '#79c0ff', Token.Literal.String.Escape: '#79c0ff', Token.Literal.String.Heredoc: '#79c0ff', Token.Literal.String.Regex: '#79c0ff', Token.Literal.Number: '#a5d6ff', Token.Comment: 'italic #8b949e', Token.Comment.Preproc: 'bold #8b949e', Token.Comment.Special: 'bold italic #8b949e', Token.Operator: 'bold #ff7b72', Token.Generic: '#e6edf3', Token.Generic.Deleted: 'bg:#490202 #ffa198', Token.Generic.Emph: 'italic', Token.Generic.Error: '#ffa198', Token.Generic.Heading: 'bold #79c0ff', Token.Generic.Inserted: 'bg:#0f5323 #56d364', Token.Generic.Output: '#8b949e', Token.Generic.Prompt: '#8b949e', Token.Generic.Strong: 'bold', Token.Generic.Subheading: '#79c0ff', Token.Generic.Traceback: '#ff7b72', Token.Generic.Underline: 'underline', Token.Text.Whitespace: '#6e7681', Token.Text: '', Token.Escape: '', Token.Other: '', Token.Keyword.Declaration: '', Token.Keyword.Namespace: '', Token.Keyword.Reserved: '', Token.Keyword.Type: '', Token.Name.Attribute: '', Token.Name.Builtin: '', Token.Name.Builtin.Pseudo: '', Token.Name.Function.Magic: '', Token.Name.Other: '', Token.Name.Variable.Class: '', Token.Name.Variable.Global: '', Token.Name.Variable.Instance: '', Token.Name.Variable.Magic: '', Token.Literal.String.Backtick: '', Token.Literal.String.Char: '', Token.Literal.String.Doc: '', Token.Literal.String.Double: '', Token.Literal.String.Interpol: '', Token.Literal.String.Other: '', Token.Literal.String.Single: '', Token.Literal.String.Symbol: '', Token.Literal.Number.Bin: '', Token.Literal.Number.Float: '', Token.Literal.Number.Hex: '', Token.Literal.Number.Integer: '', Token.Literal.Number.Integer.Long: '', Token.Literal.Number.Oct: '', Token.Operator.Word: '', Token.Punctuation: '', Token.Punctuation.Marker: '', Token.Comment.Hashbang: '', Token.Comment.Multiline: '', Token.Comment.PreprocFile: '', Token.Comment.Single: ''}

[tconbeer]

The keys of the styles dict are the Token class and its members:

from pygments.token import Token