Better documentation on usage

This library seems to be kind of unconventional on how you are supposed to add it to your project. There doesn't seem to be any module that I can directly use or anything of the like? Are we expected to just copy over the stuff from the build.zig? That seems like a lot of boilerplate.

Start by reading build.zig and the existing project documentation to understand how libvlc-zig is currently added to a Zig project. Clarify the intended integration approach and document the required setup and usage; done means a newcomer can follow the documented steps without copying unexplained boilerplate.

Written by the indexing model from the issue text.