Replace README.txt with README.md

Reviewed MR!1, the patch is not cleanly applied.

1. Project name is the first line of the document, and only level one heading (#)
2. Introduction  should come along with Project name section.
3. Use "## Table of contents" in place of "## Contents Of This File".
4. Requirements section is missing.
5. Use - (hyphen) in place of * (asterisk).

Readme.md file is not as perDrupal recommendation.

Please refer Readme.md Template : https://www.drupal.org/docs/develop/managing-a-drupalorg-theme-module-or... →

Reviewed MR!1, raised issues are now fixed and the file is updated as per readme.md file template, Hence marking it to RTBC.