Remove inverted colors in night mode

[warrenalphonso]

Description

Fixes #59

Night mode is still used, eg for keeping empty tiles black instead of white. But for color schemes, a 'small' number is assigned a light color while a 'large' number is assigned a darker color. There's no default inversion for night mode. I've left the CSS in, so maybe we can add a checkbox in Options to let the user choose Inverted colors if they'd like. (I tried doing this myself, but I kept getting a KeyError. I thought all I had to do was modify config_defaults.synced or config_defaults.profile, but neither worked. Would appreciate some help on this if it's deemed a good idea to add a checkbox in Options to let the user choose inverted colors.)

Checklist:

Please replace the space inside the brackets with an x and fill out the ellipses if the following items apply:

• [x] I've read and understood the contribution guidelines
• [x] I've tested my changes against at least one of the following Anki builds:
  • [x] Latest standard Anki 2.1 binary build
  • [ ] Latest alternative Anki 2.1 binary build
• [x] I've tested my changes on at least one of the following platforms:
  • [ ] Linux, version:
  • [ ] Windows, version:
  • [x] macOS, version: 11.2.3
• [ ] My changes potentially affect non-desktop platforms, of which I've tested:
  • [ ] AnkiMobile, version:
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[glutanimate]

Hey Warren, I really appreciate the contribution (and my apologies that it took me ages to respond)!

I agree that making this configurable would be a good idea (with the current behavior kept for existing users and perhaps even new users as people have likely gotten used to it). Given that the add-on has undergone quite a bit of refactoring recently and with more on the way in terms of how styling works, I think it's best to close this PR for now. However, I've added this to my list of things to look into as soon as that refactoring work is done (and will be happy to ping you either once the actual feature is in, or once the code is in a state where someone could reasonably pick this option up again as a PR).

Either way, thanks again for the PR!