Add rstheme_terminal_colors

[nsgrantham]

Addresses #61. I implemented your recommended changes, the rainbow parens was a helpful example to follow, thank you. I tested this on my end and it's looking good. Let me know if there is something you'd like me to take a second pass at!

[nsgrantham]

Before:

After:

Here's the code where I use rstheme_terminal_colors: https://github.com/nsgrantham/poolside-rstudio/blob/main/poolside.R

[gadenbuie]

This is great, thank you @nsgrantham! I also really like your poolside theme and I'd be happy for it to be part of rsthemes if that's something you're interested in.

I made one small suggestion to include your handle in the NEWS item.

I also need to check that the _terminal.scss partial isn't included twice when using rstheme_terminal_colors(). That might not be trivial to change; I think it's included in the base themes directly since it hasn't yet been customizable.

[nsgrantham]

Thanks, added my username to the NEWS item.

Glad you like Poolside! I'd love to add it to rsthemes, I'll open a PR when I'm done fiddling with it.

I don't entirely understand the _terminal.scss issue — does this mean the base themes need to be modified to use rstheme_terminal_colors() otherwise the partial is included twice?

[gadenbuie]

Thanks @nsgrantham and don't worry, I'll handle the _terminal.scss issue

[gadenbuie]

@nsgrantham sorry for the delay on this and thanks again for contributing the PR!

I tweaked the function signature and default arguments a bit. rstheme_terminal_colors() now picks up the theme's foreground and background colors and uses them for white and black. I also configured the args so that the _bright colors inherit from their non-bright colors, which makes it easier when you don't have a bright shade.

I also went through and added terminal colors to most themes in rsthemes, which is exciting!