Docs: Updated README.md files with TOC and best practices in Markdown

[adityakaria]

PR Type

What kind of change does this PR introduce?

• [x] Documentation changes

Motivation

Having a detailed table of contents eases the pain of having to search for information in the given file, and gives the user some helpful jump-links to different parts of the documentation.

Other changes

• Added and Removed whitespaces/blank-lines wherever necessary
• Removed trailing colon mark in headings to comply with best markdown practices

PR Checklist

• [x] I have checked that this PR does not introduce a breaking change

[adityakaria]

I notice that TOC has been in other PR's as well, one being for the same file. Just wanted to mark a point of difference that I have added a more detailed TOC.

Apart from that, I have made a couple of other changes that are unique to this PR (as mentioned in the PR description). This is my first contribution to this repository, so any suggestions would be most appreciated. Thanks!