* Make a "babashka built-in" badge available
Of note: added markdown and adoc syntaxes for badges to README.
Closes#1365
* Moved flair section under new badges section
Badges themselves act as headings under badges section.
Reworded badges text for 2 audiences.
1. The general bb user who wants to know what they mean.
2. The library author who might want to display them.
Renamed "Projects" heading to "Compatible Projects"
