Added AudioTap functionality

[bsneed]

• Added AudioTap class.
• Added AudioPlayer.audioTap variable.
• Taps are only actually changed when a AVPlayerItem is being observed.
• Clients can subclass AudioTap to retrieve the audio frame/buffer data.
• Added simple lifecycle test
• Depends on #79
• Fixes #50

[dcvz]

@bsneed your PR #73 there's also been some changes to add CI workflow for macOS. Would you mind rebasing? since your PR was squashed commit the easiest way will be to just apply the commits that changed:

git rebase --onto main HEAD~X where X is the number of commits different than the base branch that got merged.

[bsneed]

Heya @dcvz, thanks! Just updated and will keep an eye on the CI here.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 85.45455% with 8 lines in your changes are missing coverage. Please review.

Project coverage is 78.62%. Comparing base (4d3c1db) to head (2f7917b).

Files	Patch %	Lines
Sources/SwiftAudioEx/AudioTap.swift	85.71%	7 Missing :warning:
Sources/SwiftAudioEx/AudioPlayer.swift	50.00%	1 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #80      +/-   ##
==========================================
+ Coverage   78.33%   78.62%   +0.29%     
==========================================
  Files          17       18       +1     
  Lines        1288     1343      +55     
==========================================
+ Hits         1009     1056      +47     
- Misses        279      287       +8     

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[dcvz]

@bsneed I'll try to review this today or over the weekend. I've updated the example app you started to be universal for both platforms. It would be really cool to have a usage of the taps on it (a simple waveform?) in case you're interested. It's not mandatory for merge though.