Removes some quotes and unnecessary groups.

Use `\"` as it is more common in most syntaxes.
Use fixed order of quoted/unquoted key patterns in JSON5.

This directive is required only if contexts are designed to be pushed
or set onto stack directly.

Example:

main:
  - match:
    push: context

context:
  - meta_include_prototype: false

They are not needed if contexts are only `- include`ed.

Indexing top-level keys can be achieved by a selector in 
Symbol List.tmPreference even without `meta.toc-list`.

Beyond that a general purpose JSON syntax doesn't need to distinguish
between top-level and other mapping keys.

Note:
A common SymbolList.tmPreferences for all JSON dialects is sufficient.

Only contexts whose purpose is to set a meta scope should contain a
`meta` in their name.

Note:

Such contexts should use `...-body` or `...-content`.

The latter one feels more natural for comments/strings while the former
one should be preferred for code blocks.

Such contexts should use `...-body` or `...-content`.

The latter one feels more natural for comments/strings while the former
one should be preferred for code blocks.

This commit uses `{{identifier_start}}` and `{{identifier_break}}` to
push and pop `mapping-key-ecma` context on/off stack. By not consuming
anything, string interpolation is enabled for syntaxes which embed JSON.

An example might be PHP HEREDOCs.

There's no use for that syntax as it is nothing else as plain JSON.

Inheritance order is: JSON5 < JSONC < JSON

Just highlight the space illegal between two values, instead of the
whole next value.

Improve tokenization