RFE: write apkg quickstart

Add a new docs chapter with various real world examples of apkg usage in the wild.

added doc label

I would also focus on quickstart guide for those who want to simply use apkg with a project that supports it - i.e. those who don't care/know anything about packaging.

In particular, I think you can get away with just a couple setup commands:

pip3 install apkg
apkg system-setup

and then focus on just these two commands as that's all the users need:

apkg build --build-dep
apkg install

You might find some inspiration in my lightning talk slides

changed milestone to %v1.0

changed title from RFE: write apkg cookbook to RFE: write apkg quickstart