[No QA] Setup modular sass config and add color file to help site

[roryabraham]

Details

• Sets up modular sass partials
• Creates a color module so all colors reference variables
• Removes the styles for the code tag because AFAICT we have no code tags currently.

Fixed Issues

$ (partial) https://github.com/Expensify/Expensify/issues/216729

Tests

0. (you need ruby and bundler installed to do this)

1. Run:

   cd help
   bundle install
   bundle exec jekyll serve

2. Make sure the site's styles load and that all the colors look correct.

3. To convince yourself that it's working, go into the colors file and change $color-blue to #f00 and refresh the page – all the links should turn red.

[roryabraham]

This is a duplicate of #9687. Resolving conflicts was too crazy so I created a new PR

[marcochavezf]

Thanks @roryabraham! I'm going to merge it since I require these changes to fix the remaining styles (article TOC, hub pages, etc.)

@youssef-lr feel free to review it, we can address changes in a follow-up PR if needed

[OSBotify]

✋ This PR was not deployed to staging yet because QA is ongoing. It will be automatically deployed to staging after the next production release.

[OSBotify]

🚀 Deployed to staging by @marcochavezf in version: 1.1.81-0 🚀

platform	result
🤖 android 🤖	failure ❌
🖥 desktop 🖥	success ✅
🍎 iOS 🍎	success ✅
🕸 web 🕸	failure ❌

[OSBotify]

🚀 Deployed to production by @roryabraham in version: 1.1.82-5 🚀

platform	result
🤖 android 🤖	success ✅
🖥 desktop 🖥	success ✅
🍎 iOS 🍎	failure ❌
🕸 web 🕸	success ✅