Documentation on how to build and run tests for CppParser

[m-doescode]

Hello!

I've been trying to fix what I believe is a bug in the syntax implementation of attributes, but I've been unable to run tests on the project because it seems like it relies on dependencies found outside the project structure, and I've been unable to replicate them and get it working.

It would be nice if there were some instructions on this in the README or so

[satya-das]

I made a change, please take a look if that is helpful.

[m-doescode]

Ahh I'm so sorry, I completely missed the git clone for the common repository. Yes I think this new readme is much more descriptive, thank you!

P.S. All tests build and run successfully. Thank you!