Documentation index

Created by: siranipour

Hi @mariaubiali, I've fixed the issue you were talking about earlier.

The fix is as follow. When adding a new chapter do the following:

1. Create a new directory for the chapter, say get-started and inside it add all your .md files and an index.rst file.
2. Inside the new index.rst file, add all your new .md files
3. In sphinx/source/index.rst , reference the index.rst of the new chapter. So in our case, we add get-started/index.rst

I think looking at the files changed in this PR will make it clear what to do, if I've explained it badly.