Update packaging configuration and workflow

[maxrjones]

Description of proposed changes

• Upload to TestPyPI on push to main
• Remove setup.py, which is not needed for setuptools>=64.0.0
• Fix readme syntax
• Use local_scheme = "node-and-date"

Fixes #

[codecov-commenter]

Codecov Report

Merging #147 (6a5094d) into main (463227f) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #147   +/-   ##
=======================================
  Coverage   96.04%   96.04%           
=======================================
  Files           6        6           
  Lines         329      329           
  Branches       70       70           
=======================================
  Hits          316      316           
  Misses          8        8           
  Partials        5        5           

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[maxrjones]

@andersy005 or @norlandrhagen, any ideas why the package version in the "Build and Upload xbatcher to TestPyPI / Publish to Test PyPI" workflow is still {next_version}.dev{distance}+{scm letter}{revision hash}.dYYYYMMDD despite the workflow modifying pyproject.toml to include local_scheme = "no-local-version"? I'm a bit stuck on this.

The issue was keeping setup.py in the repository even though it is no longer needed with setuptools>=64.0.0