General repository improvements

[tathey1]

In descending order of importance:

• [x] Fix current documentation.

Some files/functions in the rst's are not found.

• [ ] Require docs to build successfully, probably here
• [x] Require notebooks to be stripped of output
• [x] Move tests to their respective subfolder

e.g. in hyppo

[tathey1]

@bvarjavand do you wana take the notebook strip check task? (the third one)

[github-actions[bot]]

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