Added table of contents to main readme file

[Towbee05]

Description

I added a table of contents as an entry point to the readme file

Motivation and Context

This change allows for easy navigation of the readme file

Link to issue

Fixes issue #4103

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• No code changes (changes to documentation, CI, metadata, etc)
• Dependency changes (any modification to dependencies in package.json)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[Towbee05]

Hi, I wasn't so sure if this should be a PR for feature issue or bug issue

[Towbee05]

Seeing that the contribution file is a bit more bulky than the project's readme.md file, and it has no table of contents.
Please can I add one

[Towbee05]

Also, maybe this was intentional or not, in the readme file, every section has a "##", and sub-sections have a "####", but the runtime section have a "###" which does not qualify it as either a section or sub-section. I adjusted this by making it a "##".