[tarantool-c] links to tarantool-c docs

[alg1973]

Tarantool docs connectors section should be in consistent state with tarantool-c docs:

• It should contain link to tarantool-c documentation (link to github pages): https://tarantool.github.io/tarantool-c/.
• It should contain Download, Compilation, Installation section with links to download, repo, etc.
  I think It will be good to share tarantool-c docs starting page (front page before index) with tarantol connector-c documentation section.