Add examples

[TheKitty]

Thank you for creating a pull request to contribute to Adafruit's GitHub code!
Before you open the request please review the following guidelines and tips to
help it be more easily integrated:

• No code changes, only adds demos from the Learning Center tutorial "Circuit Playground Sound and Music
• No known limitations
• tested in writing tutorial, no changes to existing code re. breaking

Thank you again for contributing! We will try to test and integrate the change
as soon as we can, but be aware we have many GitHub repositories to manage and
can't immediately respond to every request. There is no need to bump or check in
on a pull request (it will clutter the discussion of the request).

Also don't be worried if the request is closed or not integrated--sometimes the
priorities of Adafruit's GitHub code (education, ease of use) might not match the
priorities of the pull request. Don't fret, the open source community thrives on
forks and GitHub makes it easy to keep your changes in a forked repo.

After reviewing the guidelines above you can delete this text from the pull request.

Add examples from Adafruit Learning System: Circuit Playground
Sound and Music