Most developers want to have it, but few are passionate about writing and maintaining it. Be bold, and share it far and wide. Consider including a reference guide that explains the jokes, and, in the case of dead parrots, points to a YouTube video : The same goes for colloquialisms.
So it's critical that examples have been tested. About the structure Why isn't this obvious? You will look upon a file with a fond sense of remembrance.
Feel free to read this document straight through, or simply use it as a reference. By virtue of being along side the code, that documentation will be in source control. Documentation also provides a platform for your first contributions.
For some developers, reference guides are the only kind of documentation they can imagine. There's a table of contents, diagrams of the product, followed by pages describing how to use the product and then a set of troubleshooting guides at the end.
Do you really have to go through all the pains of creating several different manuals for different formats?
The voice is personal; you are speaking to a particular person, defined in the earlier persona phase.