Fix DOI and add more badges in README.md

[ericpre]

Progress of the PR

• Fix DOI in readme file,
• add more badge in readme file,
• [n/a] docstring updated (if appropriate),
• [n/a] update user guide (if appropriate),
• [n/a] added tests,
• add a changelog entry in the upcoming_changes folder (see upcoming_changes/README.rst),
• Check formatting of the changelog entry (and eventual user guide changes) in the docs/readthedocs.org:exspy build of this PR (link in github checks)
• ready for review.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.45%. Comparing base (c37013c) to head (07a4f83).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #38   +/-   ##
=======================================
  Coverage   88.45%   88.45%           
=======================================
  Files          67       67           
  Lines        7295     7295           
  Branches     1179     1179           
=======================================
  Hits         6453     6453           
  Misses        573      573           
  Partials      269      269           

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