Updates and fixes to README, index, quickstart, and usage

[philvarner]

Related Issue(s):

• n/a

Description:

• makes many references to "PySTAC Client" or "pystac-client" consistent
• adds install directions for uv and poetry
• fixes STAC Versions table in index (first row was missing a -, so that cell was rendered incorrectly
• Updated Collection Search example to an API that actually supports it (ES & PC do not). pystac encoundered an error, so changed collections to use the dict method until that gets fixed:
  • Collection.from_dict fails with type error if spatial extent is explicitly null pystac#1551
• in Usage, use conformance class enum variants instead of strings

PR Checklist:

• Code is formatted
• Tests pass
• Changes are added to the CHANGELOG

[gadomski]

I've been putting off this much needed doc refresh because I'd like to switch to markdown (#785). No objections to this cleanup, but I want to make sure you don't put too much effort into the restructured text docs?

[philvarner]

I've been putting off this much needed doc refresh because I'd like to switch to markdown (#785). No objections to this cleanup, but I want to make sure you don't put too much effort into the restructured text docs?

Noted! I mostly wanted to make sure the content of Quickstart and Usage worked and were accurate -- for example, in Quickstart, running collection search against earthsearch won't work.