[docs] add stamina video link to motivation

[sparkiegeek]

Summary

This adds an extra link to the Additional literature section of docs/motivation

Pull Request Check List

• Do not open pull requests from your main branch – use a separate branch!
  • There's a ton of footguns waiting if you don't heed this warning. You can still go back to your project, create a branch from your main branch, push it, and open the pull request from the new branch.
  • This is not a pre-requisite for your pull request to be accepted, but you have been warned.
• Added tests for changed code.
  • The CI fails with less than 100% coverage.
• New APIs are added to our typing tests in api.py.
• Updated documentation for changed code.

  • New functions/classes have to be added to docs/api.md by hand.

  • Changed/added classes/methods/functions have appropriate versionadded, versionchanged, or deprecated directives.

    The next version is the second number in the current release + 1. The first number represents the current year. So if the current version on PyPI is 23.1.0, the next version is gonna be 23.2.0. If the next version is the first in the new year, it'll be 24.1.0.

• Documentation in .md files is written using semantic newlines.
• Changes (and possible deprecations) are documented in the changelog.
• Consider granting push permissions to the PR branch, so maintainers can fix minor issues themselves without pestering you.

Hmm, should docs changes be added to the CHANGELOG?

[hynek]

hah thanks for helping me fighting the good fight! :) I mean it's already at the start of the document, but the shilling will continue until views improve!