Update parallelism example readme

[skrawcz]

Fix typo, and add new video walkthrough.

Changes

How I tested this

Notes

Checklist

• [ ] PR has an informative and human-readable title (this will be pulled into the release notes)
• [ ] Changes are limited to a single goal (no scope creep)
• [ ] Code passed the pre-commit check & code is left cleaner/nicer than when first encountered.
• [ ] Any change in functionality is tested
• [ ] New functions are documented (with a description, list of inputs, and expected output)
• [ ] Placeholder code is flagged / future TODOs are captured in comments
• [ ] Project documentation has been updated if adding/changing functionality.

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[!IMPORTANT] Fix typo and update video link in README.md for parallelism example.

• Documentation:
  • Fix typo in URL in README.md from https://burr.dagworks.io/pull/370/concepts/parallelism/ to https://burr.dagworks.io/concepts/parallelism/.
  • Update video walkthrough link in README.md from Loom to YouTube.

^{This description was created by for 4c8b4c455e786ce1a02448cbb5e1ad82b825423d. It will automatically update as commits are pushed.}

[github-actions[bot]]

A preview of is uploaded and can be seen here:

✨ https://burr.dagworks.io/pull/433 ✨

Changes may take a few minutes to propagate. Since this is a preview of production, content with draft: true will not be rendered. The source is here: https://github.com/DAGWorks-Inc/burr/tree/gh-pages/pull/433/