feat (schemes): Add Everforest color scheme

[morph626]

Added a fork of @sainnhe's Everforest color scheme (originally for Vim and VSCode) with Monokai-inspired extra highlighting for Markdown including the new python admonitions:

Dark (medium contrast) w/ extra markdown highlighting

Light variant

Admonition support

[deathaxe]

Color schemes in this package target Markdown syntax only and exist only for compatibility reasons.

Provided color schemes appear to apply rules for many syntaxes. Should those be published as separate package?

[morph626]

Color schemes in this package target Markdown syntax only and exist only for compatibility reasons.

Provided color schemes appear to apply rules for many syntaxes. Should those be published as separate package?

Oh, I didn't realise! I will remove the unrelated scopes.

[deathaxe]

1. MarkdownEditing specific color schemes start with MarkdownEditing- naming.
2. Language specific tokens may be at least useful for proper highlighting of fenced code blocks. The major point however is - instead of removing them - why not adding a new separate "Everforest" color scheme to Package Control, if rules for most languages are present anyway?
3. Color schemes in this package exist for backward compatibility and are barely (not) maintained. There's not much interest in adding more, because it is better practice to create global color schemes, which work for all use cases (writing prose in Markdown/RestructuredText/AsciiDoc/Textile/...) or coding (C/C++/Python/...).

[morph626]

Aaarh sorry, I missunderstood and thought it was a code base convention thing. I take your point and will scrap this PR in favour of its own package. Thanks for taking the time, and just wanted to ad that I've been using MarkdownEditing for ages and it is wonderful how active you guys are.