Replace README.txt with README.md

fixed, needs review.

Hi Kostiantyn

I reviewed your MR!1 and in "Project name and introduction" missing project page and issue queue, missing "Requirements" section which is required as per README.md template. → , missing "Table of contents", and text manually word-wrapped within around 80 cols. For more information, you can visit README.md → .

Thank you

Please review. Thanks.

RTBC

Thank you for your contributions.
Merged.