feat(themes): Reorganize themes Sass and add Litely Compact

[jsit]

Here's an attempt at (a) reorganizing the Sass stylesheets and (b) adding a "Litely Compact" theme (screenshots below). All I'm doing is changing the values of $spacer and $font-size-base to tighten things up, similar to what #1395 is doing.

What I'd actually like to see is each theme in its own Sass subdirectory, with the files being compiled into a flat css directory, but that would require a more thorough rewrite of the themes:build script.

Litely

Litely Compact (new)

[dankxiaobong]

Not sure if this is the right place to ask, but how did you add that theme to the user settings? I tried taking _variables.darkly.scss and darkly.scss renamed it to _variables.darkly-compact.scss and darkly-compact.scss (updated the import) and ran "yarn run themes:build". Do I have to run an additional script?

[jsit]

@dankxiaobong It's in build-themes-list.ts, but I think it will also offer any themes in the extra_themes directory.