main/sm-sparse-image-tool: new package

This small package installs a python script which can analyze and patch Android's sparse image format in order to comply with some older Samsung's variants. A good write-up by @grimler on this kind of problem is on the wiki. TLDR; some Odin loaders fail with standard android sparse image format.

The package is very small and its utility outside of pmos is limited, so I propose to only integrate it in here. One could even think of integrating it into pmbootstrap directly, as it is a vanilla python 3 script with no dependencies, but I convinced myself that a separate package was a better option.