Integrate Sparkle auto-updates for macOS Developer ID builds

New Release-DeveloperID configuration gates Sparkle behind a SPARKLE
compile flag so the App Store Release build stays Sparkle-free. Adds
SPUStandardUpdaterController wrapper, Check for Updates menu command,
Advanced Settings section with beta channel toggle, and a Ruby script
plus GitHub Actions job that signs each release and publishes the
appcast to gh-pages for consumption by Sparkle and Homebrew cask.

Yattee.xcodeproj/project.xcworkspace/xcshareddata/swiftpm/Package.resolved

@@ -1,5 +1,5 @@
 {
-  "originHash" : "50421f80aba6d558399198148743d5d479edb3f6cc10024acd55828f8cf63959",
+  "originHash" : "263c985773143365961084fa2985b6cfc81ede4476036a7c65b223ed7ced8b32",
   "pins" : [
     {
       "identity" : "mpvkit",
@@ -18,6 +18,15 @@
         "revision" : "83e19143355b02e9261edb2323b3e1e93287ebb9",
         "version" : "12.9.0"
       }
+    },
+    {
+      "identity" : "sparkle",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/sparkle-project/Sparkle",
+      "state" : {
+        "revision" : "066e75a8b3e99962685d6a90cdd5293ebffd9261",
+        "version" : "2.9.1"
+      }
     }
   ],
   "version" : 3