Restructure README.md content

[kvignesh1420]

The development section in the README.md file is not only being used to document instructions for the developers but is also used by Github Actions CI jobs. This section consumes a lot of space which might overwhelm new developers/contributors who just want to get a brief idea about the project through the README.md file.

Build Status section should be updated as new datasets have been added and the python version for CI builds have changed.

Suggested plan:

• Create a new reference for developers in docs/ named developer.md which will contain the development section. This file can be used by the Github Actions instead of README.md ([docs] Restructure README.md content #1257)
• Update/Refactor the content and tables in Build Status section. ([docs] Restructure README.md content #1257)

Will create PR's as per these items.
cc: @yongtang @terrytangyuan @BryanCutler @vlasenkoalexey for suggestions.

[yongtang]

Sounds good to me 👍