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/Localizable.xcstrings

@@ -5142,6 +5142,16 @@
         }
       }
     },
+    "menu.app.checkForUpdates" : {
+      "localizations" : {
+        "en" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Check for updates..."
+          }
+        }
+      }
+    },
     "menu.app.settings" : {
       "localizations" : {
         "en" : {
@@ -14338,6 +14348,36 @@
         }
       }
     },
+    "settings.updates.footer" : {
+      "localizations" : {
+        "en" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Check for and install new versions of Yattee. Beta updates include prereleases."
+          }
+        }
+      }
+    },
+    "settings.updates.receiveBeta" : {
+      "localizations" : {
+        "en" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Receive beta updates"
+          }
+        }
+      }
+    },
+    "settings.updates.title" : {
+      "localizations" : {
+        "en" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Updates"
+          }
+        }
+      }
+    },
     "settings.videoActions.header" : {
       "localizations" : {
         "en" : {