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