Jsonparse

Added a new `find_value` function. This will return all keys with the associated value.

A good example for this is to find all keys that have a null value, ie in the library, simply `find_value(data, False)`

See the README here:
- https://github.com/ctomkow/jsonparse?tab=readme-ov-file#find_value

Offical python 3.12 support. Updated docs and tests.

- Added functions so no need to create a Parser object, simply import. However, the Parser object still works fine.

`from jsonparse import find_key, find_keys, find_key_chain, find_key_value`

- Fixed install issue which incorrectly marked directories tests and docs as packages

- python 3.6, 3.11 support
- cli interface added. Now use jsonparse as a cli tool for JSON manipulation

- Final pre-release of cli tool update