Add support for diminished chords

[CasP0]

Add support for diminished chords in the arpeggios application.

• Notes.js

  • Add a new chord type "diminished" to the Notes object.
  • Add a loop to generate diminished chords for each key in Positions.majorOrder.
  • Add the generated diminished chords to the Notes.diminished object.

• package.json

  • Add a new dependency for "diminished-chords" library.

• README.md

  • Update the build instructions to include the new dependency.
  • Add a section listing the new dependency.

---

For more details, open the Copilot Workspace session.

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.