Clarify about poetry

[elsiehupp]

I vaguely remembered the Poetry installation being somewhat weird, so I checked the documentation, and it says to use pipx instead of pip:

pipx install poetry

pipx appears to have its own setup process (with different instructions depending platform). (That is, pipx is apparently not installed by default with Python.)

I think what I was remembering was that previously Poetry used curl for installation, but pipx appears to abstract away some of the complexity.

[robkam]

pipx installs and runs Python applications in isolated environments. As yet we've not yet done anything like that with MediaWiki Dump Generator.

[robkam]

Perhaps including instructions for installing poetry is getting out of scope?

[robkam]

Instructions for installing poetry is out of scope.