Documentation updates: contributor's guide, notebook name standardization, hiding code cells

[TeaganKing]

This PR will address issues raised in #146, #96, and #60. The key items it addresses are as follows:

1. Provide documentation on how to hide code cells
2. Provide suggestions for notebook names
3. Move contributor's guide from wiki to documentation page
4. Link to contributor's guide in 'how to add notebooks' page
5. Update a few outdated links and clarify a few steps
6. Clarify instructions on pre-commit installation
7. Update PR checklist to make pre-commit clearer and remove irrelevant items

Still need to do:

• Remove wiki contributor's guide once this is merged in
• Check with CUPiD team that notebook naming suggestion is reasonable (will check in next meeting and can edit later, too)
• Hide any additional cells in key_metrics examples that need hiding

• Have you followed the guidelines in our Contributor's Guide (including the pre-commit check)?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Does your submission pass tests?
• Have you lint your code locally prior to submission?
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you successfully tested your changes locally?

[TeaganKing]

Here is a screenshot of the build that implements the current changes.

[mnlevy1981]

This is a huge update for the documentation, and it looks great! A few small tweaks to think about, but overall 👍

[TeaganKing]

Thanks for these suggestions, @mnlevy1981 . FYI I also re-built and fixed a few links, and it is building properly. The documentation still looks the same as the above screenshot.

[mnlevy1981]

LGTM!