* Update authors to "jrnl contributors" to comply with GPL3
* Include jrnl email address with contributors
* Include GPL notice in jrnl --version
* Apply consistent copyright and license to all Python files
* Add copyright and license to documentation
* Add copyright and license to docs theme
* Wiping poetry cache to try to resolve a test issue
* Testing with Python 3.9.0 in attempt to bypass GitHub Actions failure in 3.9.1
* make format
* Exclude Windows Python 3.9 build which is failing due to a GitHub Actions problem
* Modify testing to get around this 3.9 issue...
* Fix exclude
It's not our main branch anyway, and "release" makes it more clear what
it's for. There's an industry-wide trend to move away from terms that
invoke master/slave relationships in order to make members of
marginalized populations slightly less uncomfortable.
* Include information about branching strategy
* Re-organize documentation and include information on testing
* Use gerund form in Contributing headlines
* Fix markdown links and expand developing documentation
* Add pipx link and explain test code structure
* Include pull request process in CONTRIBUTING
* Update CONTRIBUTING with small changes from PR review
* Mention failing tests in CONTRIBUTING
* Add information for developers about issue labels
