Replace README.txt with README.md

Added readme.md file to the code base in accordance to readme.txt

Please review and suggest if any other change required,
Moving the issue to needs review.

Reviewed MR!87, Kindly follow the format given below:

README format
Drupal recommends the following README formatting:

Headings capitalized with an initial capital, following standard English sentence rules
Headings prefixed with #/##/### to indicate level of heading (h1/h2/h3) followed by a blank line
Project name is the first line of the document, and only level one heading (#)
Two lines prior to ##/### headings
No leading or trailing spaces
Bulleted lists denoted by dashes (-)
Ordered lists use "1", for easier updates and to avoid errors (see Configuration)
Nested lists indented with 4 spaces
Links should have a meaningful link text, for example:
[Drupal](https://www.drupal.org/) (i.e. not just the URL)
Text manually word-wrapped within around 80 cols

Please review. Thanks.

Verified the MR !87, the readme.md file is updated as per standard. Added screenshots for reference, RTBC++

Reviewed MR!87, the file is updated as per the readme.md template instruction.
Hence marking it to RTBC.