Replace README.txt with README.md

Hi Team

I change the README.md file according to template provide by drupal org and created a patch file can review.

thanks

@dinesh Getting the error
error: README.md: No such file or directory

I applied patch #3 getting error:

error: README.md: No such file or directory

ravi kant → made their first commit to this issue’s fork.

ravi kant → changed the visibility of the branch 2.0.0-beta1 to hidden.

Created READDME.md file and generated readme file.

Reviewed MR!1, the file is updated as per the readme.md file template.
Hence marking it to RTBC.