Documentation updates required to use GitHub rather than SVN

[gfenoy]

I noticed when going in the contributor guide that it would require some updates to replace SVN by GitHub.

The pages from the contributor guide that needs rewrite:

• https://github.com/ZOO-Project/ZOO-Project/blob/main/docs/contribute/code.rst
• https://github.com/ZOO-Project/ZOO-Project/blob/main/docs/contribute/doc.rst
• https://github.com/ZOO-Project/ZOO-Project/blob/main/docs/contribute/dev.rst
• https://github.com/ZOO-Project/ZOO-Project/blob/main/docs/contribute/release.rst

Other:

• https://github.com/ZOO-Project/ZOO-Project/blob/main/docs/install/download.rst
• https://github.com/ZOO-Project/ZOO-Project/blob/main/docs/install/debian.rst

[gfenoy]

This should be solved with fbb0c3db.

Documentation is now hosted using GitHub pages available here.

Any feedbacks are welcome.

[gfenoy]

The web site has been updated to include these new links.