Add README.md and CONTRIBUTING.md, refs #17189
Add back submodule for less v1.3.3.

This is needed to get dijit/themes/claro/compile.js and dojox/trunk/mobile/themes/utils/compile.sh
working again.  Might be possible to install less via "npm install" instead but this is the path of
least resistance.  Less submodule was originally part of 8525a1a318033ea75bef49c54c1e91688aad49e9.
Update build release script for Git. Refs #17176.