Add surge-synthesizer 1.6.0 (#64210)

Surge Synthesizer is a VST2/VST3/AU audio plugin which implements
a multi-oscillator digital synthesizer you can use in programs
such as Logic, GarageBand, Reaper, Bitwig and more. In september
2018 an incomplete version 1.6 was opensourced under GPL3 and in the
intervening 6 months, we have fixed bugs, added features and so on.
The synth is now at a stable 1.6.0 release and we would like to
include this in homebrew using the token 'surge-synthesizer' and
the version 1.6.0.

Casks/surge-synthesizer.rb

@@ -0,0 +1,19 @@
+cask 'surge-synthesizer' do
+  version '1.6.0'
+  sha256 'f60d2006cc9121249c7284bf8af694a00dd0e6713620662e2538e1937688bcaa'
+
+  # github.com/surge-synthesizer/releases was verified as official when first introduced to the cask
+  url "https://github.com/surge-synthesizer/releases/releases/download/#{version}/Surge-#{version}-Setup.dmg"
+  appcast 'https://github.com/surge-synthesizer/releases/releases.atom'
+  name 'Surge - a Digital Synthesizer'
+  homepage 'https://surge-synthesizer.github.io/'
+
+  pkg "Surge-#{version}-Setup.pkg"
+
+  uninstall pkgutil: [
+                       'com.vemberaudio.vst2.pkg',
+                       'com.vemberaudio.vst3.pkg',
+                       'com.vemberaudio.au.pkg',
+                       'com.vemberaudio.resources.pkg',
+                     ]
+end