[FEATURE]: Add contribution guidelines documentation

[evan-palmer]

Is your feature request related to a problem? Please describe

There is no documentation discussing the project contribution guidelines. This makes it difficult for new developers to approach the project and contribute new features.

Describe the solution you'd like

Write a new contribution guidelines document that describes the steps to contribute to the project.

Describe alternatives you've considered

This could alternatively be included only in the developer documentation; however, given the goal of hosting only user documentation and generating doxygen documentation manually, it would likely be better to have an independent document.

Implementation Ideas

Add a CONTRIBUTING.md document that defines the steps to contribute and the types of contributions that are accepted.

Additional context

• pymavswarm example