CI/CD Updates and Fixed A* Fork

[bluemellophone]

This PR fixes all CI/CD workflows and migrates the pyastar2d dependency to a temporary fork (see hjweide/pyastar2d#47 for a PR in the upstream project)

Changelog

Added

• Added development instructions and a description of the spectrogram generation process to README.rst
• Added todo items to the ISSUES.rst

Changed

• Fixed macOS-specific datatype bugs in batbot/spectrogram/__init__.py and other various improvements
• Updated the GitHub action workflows with improved triggers and updated versions of all marketplace process steps
• Set the default output mode to debug=False
• Fixed the metadata khz JSON key unit to hz
• Updated .gitignore for project build folders
• Updated the runtime and optional requirements list
• Updated the wheel requirements in setup.cfg

Removed

• Removed the pyastar2d TPL folder, migrated to a fork (https://github.com/bluemellophone/batbot-pyastar2d)
• Removed the separate pyastar2d dependency build step in Dockerfile
• Removed pyproject.toml from the MANIFEST.in
• Removed defunct tests

[stoutta6]

All comments addressed in meeting. Switched to using global threshold in compressed spectrogram generation.