Write guides on how to contribute

Currently, the Get Involved page is not very detailed. It'll be nice to have detailed guides on how to contribute to Briar, depending on skills and interests.

Proposed structure

Make a donation
Share your experience:
    - Report bugs
    - Test Briar
    - Provide feedback
    - Help other Briar users
Contribute your language skills:
    - Improve documentation
    - Write news and blog posts
    - Translate
Promote Briar:
    - Write press releases
    - Design outreach material
    - Talk about Briar at events
Contribute your computer skills:
    - Work on the source code
    - Improve Briar's infrastructure
    - Improve the website
    - Design graphics
    - Improve UX
Reference documents:
    - Code of conduct
    - Merge policy
    - Release process & schedule
    - Glossary
    - Logo
    - Developer docs
Contributor tools:
    - Source code: Git repositories
    - Roadmap
    - Building the app from source
    - Starter tasks for new contributors
    - Git workflow
    - Join the mailing list