Packaging: Add a ZipApps section

[jhermann]

I could do a PR based on the following sources, assuming you'd merge it (i.e. the effort won't be wasted).

• Building Zipapps (PEP 441)
• Packaging Python EXecutables (PEX)
• Installation With PEX
• Enabling Easy Zipapp Installs on Windows
• Bundling Python Dependencies in a ZIP Archive

[bzaczynski]

That would be so useful to have it in one place! I had to literally look up some this information a couple of days ago. Sure, go ahead and make some new content if you can. It most definitely won't be a wasted effort. I'll appreciate that!

[jhermann]

One open question is if the content warrants a whole chapter besides packaging and freezing, or add it to packaging.

[bzaczynski]

Either way will work for me, but personally I'd rather put it under the existing "packaging" section. Did you have a specific title for this new section in mind?

[calwarhurst]

To revisit this, Python has included zipapp since version 3.5. I think it belongs in or around freezing. Would a PR be considered for this?