Add readthedocs

[kaitj]

Proposed changes

This PR adds in searchable documentation via readthedocs. From the readthedocs side, I've hidden the latest version, which points to main and instead defaulted the docs to stable, which should always point to the most recently released tagged version. In addition, I've enabled version tagging and activation so that there will be documentation specific to each released version - these tagged versions can be manually removed from the doc sidebar if needed. Lastly, PR builds have been enabled, so there will be a preview of the documentation for each PR.

Also using this PR to fix spelling in the PR template (functionalitiy -> functionality)

Types of changes

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

• [ ] Bugfix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [x] Other (if none of the other choices apply)

Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you are unsure about any of the choices, don't hesitate to ask!

• [ ] Changes have been tested to ensure that fix is effective or that a feature works.
• [ ] Changes pass the unit tests
• [ ] Code has been run through the poe quality task
• [x] I have included necessary documentation or comments (as necessary)
• [ ] Any dependent changes have been merged and published

Notes

All PRs will undergo the unit testing before being reviewed. You may be requested to explain or make additional changes before the PR is accepted.

[kaitj]

Should be good for a review now. Some of the images may not render until merged since I put the expected path in. I found that relative paths didn't work in the preview.