Add sphinx-codeautolink to docs

[btjanaka]

Description

sphinx-codeautolink links functions in code examples to their respective definitions. This plugin works out of the box.

TODO

Questions

Status

• [x] I have read the guidelines in CONTRIBUTING.md.
• [x] I have formatted my code using yapf
• [x] I have tested my code by running pytest
• [x] I have linted my code with pylint
• [x] I have added a one-line description of my change to the changelog in HISTORY.md.
• [x] This PR is ready to go