split the readme putting the development part into contributing.md - add a support table

[JeffGarland]

A recent PR for examplar split the part of the documentation for thos contrubuting to the library into it's own markdown file - we should adopt that here. Also another newer feature of docs is to have a supported compilers table like this one in beman.scope

https://github.com/bemanproject/scope?tab=readme-ov-file#integrate-bemanscope-into-your-project