Docs: Link to datasets for ptychography

[uellue]

Drive-by: Some small infra tweaks

Refs https://github.com/LiberTEM/LiberTEM/issues/1069

Contributor Checklist:

• [x] I have added myself to the creators.json file
• [x] I have added a changelog entry for my contribution
• [x] I have added/updated documentation for all user-facing changes
• [N/A] I have added/updated test cases

[codecov[bot]]

Codecov Report

Merging #57 (f5b4f07) into master (e20812b) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #57   +/-   ##
=======================================
  Coverage   64.08%   64.08%           
=======================================
  Files           8        8           
  Lines         323      323           
  Branches       38       38           
=======================================
  Hits          207      207           
  Misses        104      104           
  Partials       12       12           

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