Implement separate TestPyPI upload workflow

[nfelt14]

Proposed changes

A separate workflow for uploading to test.pypi.org was needed to simplify the process.

Types of changes

What types of changes does your code introduce?
Put an x in the boxes that apply

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Functionality update (non-breaking change which updates or changes existing functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• CI/CD update (an update to the CI/CD workflows, scripts, and/or configurations)
• Documentation update (an update to enhance the user experience when reading through the docs)

Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your code.

• I have followed the guidelines in the CONTRIBUTING document
• I have signed the CLA
• I have checked to ensure there aren't other open Pull Requests for the same update/change
• I have performed a self-review of my code
• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• Basic linting passes locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have added necessary documentation (if appropriate)
• I have updated the Changelog with a brief description of my changes

[codecov]

Codecov Report

Merging #20 (329d867) into main (2829a09) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##              main       #20   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          168       168           
  Lines         3756      3756           
  Branches       646       646           
=========================================
  Hits          3756      3756           

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