Transition most text README files to markdown or restructured text format so will be visualized in github/VS code

[ekluzek]

Many of our README files are in raw text format. Since github will visualize markdown or restructured text, we should update them to one of those formats. Which will make them easier to read on either github or VS code, but still readable in raw text format. This will make URL's proper links and issue or PR's links as well.

[wwieder]

let's do this in markdown