add page creation and update dates to footer

[williambdean]

Description

This adds footer for dates: "Created: | Last updated: "

Is there an appetite for this?

Related Issue

• Closes #
• Related to #

Checklist

• Checked that the pre-commit linting/style checks pass
• Included tests that prove the fix is effective or that the new feature works
• Added necessary documentation (docstrings and/or example notebooks)
• If you are a pro: each commit corresponds to a relevant logical change

Type of change

• New feature / enhancement
• Bug fix
• Documentation
• Maintenance
• Other (please specify):

[williambdean]

I was considering this repo: https://sphinx-git.readthedocs.io/en/latest/index.html

However, it didn't seem to provide the information that I wanted. However, I don't know the sphinx ecosystem that well. Anyways, this is an implementation.