Add comprehensive-rust and mdbook-i18n-helpers

[mgeisler]

These are two repositories that I maintain. We would be happy to mentor people.

Repository information

The repository has:

• [x] At least three issues with the good first issue label.
• [x] At least 10 contributors (mdbook-i18n-helpers is a spin-off from comprehensive-rust and maintained by the same group of developers)
• [x] Detailed setup instructions for the project.
• [x] CONTRIBUTING.md
• [x] Actively maintained.