docs: Documentation Improvements

[shikharvashistha]

This pull adds the following changes to our current documentation:

1. Indexing Improvements
2. Introduced C++ syntax highlighting
3. Aggregated contributors list at the end
4. Addition of basic tutorial
5. Format Improvements

The preview of changes can be found here.

[github-actions]

This Pull request Passed all of clang-tidy tests. 👍

[amitsingh19975]

I loved the documentation, but there are some minor things that make it harder to read and reason about.

1. Except for Tensor, every class' constructor, assignment, modifying functions, etc., are mixed.
2. It is hard to find function names from convoluted prototypes. It would be better if we have separate columns with names, return types and prototypes.

@bassoy, what do you think of the second point?