Docs updates

[ihsaan-ullah]

1. At multiple places we have %3A in some urls. We should remove this
2. We have Governance, privacy policy and About still in the old wiki. We may want to move them to dedicated pages like CONTRIBUTING.md. After that we should change the links too everywhere
3. We have two folders for docs: documentation and docs. We should check docs and move it to documentation or remove it.

[ihsaan-ullah]

There is a PR about point #2. Point #3 should be discussed and can be moved to a separete repo like my leaderboard repo here: https://github.com/ihsaan-ullah/codabench-leaderboard-fetch