Adds catalog-info.yaml and updates README as per OEP-55

[pomegranited]

Description:

Following the steps in How to maintain a repo, this PR:

• adds catalog-info.yaml to record maintainership in Backstage
• updates README.rst to use current cookiecutter format.
• moves LICENSE to LICENSE.txt to match cookiecutter defaults.
• Fixes quality issues in CHANGELOG
• fixes bugs to allow use of manage.py shell
• minor updates to PR template

JIRA:

Private-ref: FAL-3684

Testing instructions:

To test this change, please follow the updated README#getting-started-with-development.

Author Notes & Concerns:

This repo has docs, but they're not published to docs.openedx.org yet.

Could someone with access please add them? Procedure noted here: https://openedx.atlassian.net/wiki/spaces/DOC/pages/21627535/Publish+Documentation+on+Read+the+Docs

Merge checklist:

• All reviewers approved
• CI build is green -- enough. Can't codecov this change without code changes.
• Version bumped - N/A
• Changelog record added - N/A
• Documentation updated (not only docstrings)
• Commits are squashed

Post merge:

• Create a tag - N/A
• Check new version is pushed to PyPi after tag-triggered build is finished. - N/A
• Delete working branch (if not needed anymore)

[openedx-webhooks]

Thanks for the pull request, @pomegranited! Please note that it may take us up to several weeks or months to complete a review and merge your PR.

Feel free to add as much of the following information to the ticket as you can:

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Please let us know once your PR is ready for our review and all tests are green.

[sarina]

A couple suggestions, merge when you're ready.

[sarina]

This link doesn't work for me

[pomegranited]

Ya -- I need someone with access please add them? Procedure noted here: https://openedx.atlassian.net/wiki/spaces/DOC/pages/21627535/Publish+Documentation+on+Read+the+Docs

(same issue for edx-submissions, btw)

[sarina]

Hmm, that page is archived and I don't know the current procedure. @feanil can you help out here?