Add Developer Guide

[fdmalone]

Would be helpful to add some quick development guid to the docs, which might include:

• [ ] available bit utility functions for testing
• [ ] Other useful utility functions for testing
• [ ] Common errors (I have a running list of mistakes I keep making)
• [ ] Helpful hidden gems

[fdmalone]

• [ ] Splits and joins

[fpapa250]

• [ ] Style guide for function signatures
• [ ] List of functions that are desired for a bloq (signature, build_composite_bloq, build_call_graph, etc.)
• [ ] Writing unit tests for a bloq