Add extra index for the Algorithms, Distributions and Util

[Frank-7]

Where?

They need a collapsible tree on the left displaying each of them and adding capabilities to browse them directly.

Who?

Users

What?

Add browsing capabilities on the index panel to be able to get to each of the algorithms, distributions and util directly.

[dnabanita7]

I am taking up the issue.

[dnabanita7]

In my understanding, there is pydp.rst which has listed Algorithms, Distributions, Util and index.rst has already included pydp.rst file in the toctree. I think this has been resolved.

[dnabanita7]

cc @chinmayshah99 @Frank-7