docs(README.md): change some badges sources

[mdevolde]

docs(README.md): change some badges sources

Why the pull request was made

To ensure displaying information from reliable sources in the README.

Summary of changes

• Now display the package pypi version from shields.io.
• Now display download stats from shields.io, and redirect to pypistats.org.

Screenshots (if appropriate):

Not applicable.

How has this been tested?

Not applicable.

Resources

• https://github.com/psf/pypistats.org
• https://github.com/badges/shields

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update (changes to documentation only)
• Refactor / code style update (non-breaking change that improves code structure or readability)
• Tests / CI improvement (adding or updating tests or CI configuration only)
• Other (please describe):

Checklist

• Followed the project's contributing guidelines.
• Updated any relevant tests.
• Updated any relevant documentation.
• Added comments to your code where necessary.
• Formatted your code, run the linters, checked types and tests.