chore(plugins): stop tracking generated example/tvos build artifacts

`example/tvos/Flutter/GeneratedPluginRegistrant.swift` and friends are
generated by `flutter-tvos` at build time, but were committed across
all 11 plugin examples as empty stubs from the pre-federated-plugin
era. The CLI's build pipeline only regenerates these files when
*missing* — so the stale committed stubs were left in place on every
build, and every federated tvOS plugin with `dartPluginClass:` was
silently dropped from the registrant. Runtime symptoms:
`MissingPluginException` for `shared_preferences`, `audioplayers`,
`video_player`; `Bad state: <X>Platform.instance must be set` for the
new async APIs.

Adds a per-plugin `.gitignore` rule excluding the generated files
(`GeneratedPluginRegistrant.swift`, `Generated.xcconfig`,
`flutter_export_environment.sh`, `Podfile.lock`, `Pods/`, `.symlinks/`)
and untracks the stale stubs so the next clean build produces a
proper registrant.

No plugin source code change — Dart, Swift, pubspec, lib/, ios/, tvos/
all untouched. iOS/Android/macOS/web users see zero behavioural
difference; existing pub.dev versions remain valid.

Author: MAUstaoglu

packages/audioplayers_tvos/.gitignore

@@ -20,3 +20,13 @@ tvos/Flutter/Flutter.podspec
 
 # macOS
 .DS_Store
+
+# Generated by flutter-tvos at build time — should never be committed.
+# Checking in stale empty stubs causes plugin registration to silently fail
+# because the build pipeline only regenerates these when missing.
+example/tvos/Flutter/GeneratedPluginRegistrant.swift
+example/tvos/Flutter/Generated.xcconfig
+example/tvos/Flutter/flutter_export_environment.sh
+example/tvos/.symlinks/
+example/tvos/Pods/
+example/tvos/Podfile.lock

packages/audioplayers_tvos/example/tvos/Flutter/GeneratedPluginRegistrant.swift

@@ -20,3 +20,13 @@ tvos/Flutter/Flutter.podspec
 
 # macOS
 .DS_Store
+
+# Generated by flutter-tvos at build time — should never be committed.
+# Checking in stale empty stubs causes plugin registration to silently fail
+# because the build pipeline only regenerates these when missing.
+example/tvos/Flutter/GeneratedPluginRegistrant.swift
+example/tvos/Flutter/Generated.xcconfig
+example/tvos/Flutter/flutter_export_environment.sh
+example/tvos/.symlinks/
+example/tvos/Pods/
+example/tvos/Podfile.lock

packages/connectivity_plus_tvos/.gitignore

@@ -20,3 +20,13 @@ tvos/Flutter/Flutter.podspec
 
 # macOS
 .DS_Store
+
+# Generated by flutter-tvos at build time — should never be committed.
+# Checking in stale empty stubs causes plugin registration to silently fail
+# because the build pipeline only regenerates these when missing.
+example/tvos/Flutter/GeneratedPluginRegistrant.swift
+example/tvos/Flutter/Generated.xcconfig
+example/tvos/Flutter/flutter_export_environment.sh
+example/tvos/.symlinks/
+example/tvos/Pods/
+example/tvos/Podfile.lock

packages/connectivity_plus_tvos/example/tvos/Flutter/GeneratedPluginRegistrant.swift

@@ -20,3 +20,13 @@ tvos/Flutter/Flutter.podspec
 
 # macOS
 .DS_Store
+
+# Generated by flutter-tvos at build time — should never be committed.
+# Checking in stale empty stubs causes plugin registration to silently fail
+# because the build pipeline only regenerates these when missing.
+example/tvos/Flutter/GeneratedPluginRegistrant.swift
+example/tvos/Flutter/Generated.xcconfig
+example/tvos/Flutter/flutter_export_environment.sh
+example/tvos/.symlinks/
+example/tvos/Pods/
+example/tvos/Podfile.lock

packages/device_info_plus_tvos/.gitignore

@@ -20,3 +20,13 @@ tvos/Flutter/Flutter.podspec
 
 # macOS
 .DS_Store
+
+# Generated by flutter-tvos at build time — should never be committed.
+# Checking in stale empty stubs causes plugin registration to silently fail
+# because the build pipeline only regenerates these when missing.
+example/tvos/Flutter/GeneratedPluginRegistrant.swift
+example/tvos/Flutter/Generated.xcconfig
+example/tvos/Flutter/flutter_export_environment.sh
+example/tvos/.symlinks/
+example/tvos/Pods/
+example/tvos/Podfile.lock