Improve Contribution documentation

[elizalflores]

I believe the project README.md and CONTRIBUTING.md should include more clarifying information and directions for developers on how to contribute.

Currently there is further, nested documentation on how to contribute to the project located in the TinyWebEx project.

I plan to modify the README.md and CONTRIBUTING.md to help give more information about these additional guidelines.

[rugk]

Sure do a PR; but from your description it is not really clear what you want to modify.

Note the big parts should be into the "nested" TinyWebEx contrib doc, as this applies to all extensions and I don't want to maintain that change in each extension. So maybe your PR should be done there, depending on the changes.