Update docs to mention ArviZ partnership

[sethaxen]

Following #25 (comment), this PR updates the readme and docs to mention that this is a joint project between Turing and ArviZ.

It also

• adds a NumFOCUS badge (on all the ArviZ component packages, since ArviZ is sponsored)
• adds me as coauthor
• adds an admonition for the less common (and not-so-well-maintained) diagnostics.

[github-actions]

Pull Request Test Coverage Report for Build 6410469635

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 96.655%

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Totals
Change from base Build 6410306834:	0.0%
Covered Lines:	838
Relevant Lines:	867

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💛 - Coveralls

[codecov]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (a72f954) 96.65% compared to head (ce863ef) 96.65%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #103   +/-   ##
=======================================
  Coverage   96.65%   96.65%           
=======================================
  Files          11       11           
  Lines         867      867           
=======================================
  Hits          838      838           
  Misses         29       29           

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[yebai]

Thanks, @sethaxen, for the dedicated work!