Increase discoverability of projects with issues that need help

[freak4pc]

This continues discussion of #71, initially started by @pedrommcarrasco.

The TL;DR is - we need a good way to indicate to people if some projects have issues that need contributions. This helps the projects, but also helps contributors become more involved and pull in more new contributors.

Here is my proposed solution for this issue:

• Mark issues with help wanted and good first issue. This is something anyone can definitely help with in the "moderation" side, if they have the time or just see an issue without a tag. This will also help on the GitHub side of things.

• On the web side, have the script populate the number of issues as well, and then we can have a colored badge (red, orange, yellow, green) based on the number of open issues that need external help (for example green: 0, yellow, 0-3, orange: 3-10, red: >10, but we can experiment with these numbers later). If colors are scary we can go with some other visual indication :)

We can also add an explanation on the top of the page so people understand these badges, and they would link directly to the issues that need help (e.g. marked with these tags).

Since most issues don't have these tags used we might want to start with a version that counts all issues for a repo instead of just those with these specific tags, and later migrate to the tag-based solution when those become more common.

Would appreciate feedback from @RxSwiftCommunity/contributors if any :)
Shai.