How to contribute incrementally to Theoretical CS - similar to github
As mentioned in a comment above, you can contribute to the TCS Wikipedia Project led by Shuchi Chawla:


  Wikipedia is a great resource for people outside of the TCS community to learn about TCS topics, and provides an educational and outreach opportunity for our community. Our community should ensure that important TCS topics get adequate and accurate coverage in Wikipedia through articles written by experts. Unfortunately, writing or editing articles for Wikipedia, and ensuring that the edits are not overwritten, can be a daunting task. It is a task best addressed as a community effort rather than by a few individuals.