Replace README.txt with README.md and update README.md file

Created MR for the issue.
Please review.

The patch works fine and moving it to RTBC.

1. Configuration is missing. 
2. [project page] and [issue queue] is missing.
3. Change "## Contents of this file" to "## Table of content".

Configuration is already addressed in the usage section.

1. [Views jcSlider](https://www.drupal.org/project/views_jcslider). - Here instead of [Views jcSlider], it should be written as [project page]

I reviewed MR!1, and the file is updated as per the readme.md file template.
Hence, marking it as RTBC.

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