docs: added PyPI downloads badges

[juarezr]

This PR has the objective of .

Changes

1. Added PyPI downloads badge

Checklist

Use this checklist to ensure the quality of pull requests that include new code and/or make changes to existing code.

• [ ] Source Code guidelines:
  • [ ] Includes unit tests
  • [ ] New functions have docstrings with examples that can be run with doctest
  • [ ] New functions are included in API docs
  • [ ] Docstrings include notes for any changes to API or behavior
  • [ ] All changes are documented in docs/changes.rst
• [x] Versioning and history tracking guidelines:
  • [x] Using atomic commits whenever possible
  • [x] Commits are reversible whenever possible
  • [x] There are no incomplete changes in the pull request
  • [x] There is no accidental garbage added to the source code
• [ ] Testing guidelines:
  • [ ] Tested locally using tox / pytest
  • [X] Rebased to master branch and tested before sending the PR
  • [x] Automated testing passes (see CI)
  • [x] Unit test coverage has not decreased (see Coveralls)
• [ ] State of these changes is:
  • [ ] Just a proof of concept
  • [ ] Work in progress / Further changes needed
  • [x] Ready to review
  • [x] Ready to merge

[coveralls]

Pull Request Test Coverage Report for Build 8715808718

Details

• 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 91.072%

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Totals
Change from base Build 8288788130:	0.0%
Covered Lines:	13352
Relevant Lines:	14661

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💛 - Coveralls