Add Synth1 Audio Unit and VST

[joshka]

Includes the new artifacts to represent a symlink to the ~/Library/Audio/Plug-Ins/{VST,Components} folders.

[adidalal]

On hold until #15643 is merged.

The PR will likely need to be redone at that point so that only the two synth1-Cask related files are modified.

[joshka]

Gotcha - thanks.

[adidalal]

@joshka #15643 is now merged and the documentation updated accordingly.

Please either rebase or make a new PR with only the two Cask files - synth1-au.rb and synth1-vst.rb.

Additionally, please change the cask header lines.
Example: cask 'dropbox' do

Also I noticed you were using joshka.github.fake@joshka.net.fake as the commit email. If you change your local git commit email to joshka@users.noreply.github.com, it will link your commits to your Github user page properly, while still hiding your email address.

[jawshooah]

Thank you for the contribution. It needed some fixes, so they were made in abe5fa7. Your contribution is still included (and still credited to you), with the appropriate modifications. Please feel free to ask about any of the changes.

[joshka]

Thanks guys