Update README.md to follow Drupal standards in regards to this file

Problem/Motivation

I was looking at the README.md file and it doesn't quite follow the Drupal standards in regards to this file: https://www.drupal.org/docs/develop/managing-a-drupalorg-theme-module-or... →

It lacks the intro text and other required sections: https://git.drupalcode.org/project/many_selects/-/blob/2.0.x/README.md?r...

It would be great to refactor this file to follow the Druplal guidelines.

Steps to reproduce

Look at the README.md file

Proposed resolution

Refactor the file

Remaining tasks

N/A

User interface changes

N/A

API changes

N/A

Data model changes

N/A