Relative JSON Pointer implementation in Python

WARNING: This project is in the earliest stages of development, although I am reasonably sure that it works. I intend to polish it and publish it properly during Summer 2022, particularly if I can get the following issues resolved in a new draft release:

• #1235 or #1236, which are two proposals to allow using Relative JSON Pointer's # opeator on JSON Pointers that use the - special index operator. Technically, #1235 would be needed in order for the way this library works to be considered correct, as it is implemented by resolving against a base pointer and applying the resulting RFC 9601 JSON Pointer rather than directly operating on an instance. This is useful as parent traversals are difficult in most in-memory representations of JSON (although see jschon's RelativeJSONPointer and JSON classes for an implementation using a parent-aware data structure).

• #1175, which clarifies that index manipulation and # can be used together, even though we forgot to put it in the ABNF.

And possibly anything else tagged with "rel json pointer".

Please do feel free to file issues if you notice a problem or have a need for it to be on PyPI sooner.