[Monorepo] Add PAPER_ENABLED env variable (#3510)

## Description

This PR adds `PAPER_ENABLED` environmental variable in order to easily switch to old architecture in `ExpoExample`. It also adds CIs that test paper build on both platforms. 

## Test plan

Verified in `App.tsx` with the following snippet:

```jsx
const uiManager = global?.nativeFabricUIManager ? 'Fabric' : 'Paper';
console.log(`Using ${uiManager}`);
```

Check that CIs pass.

Author: m-bert

.github/workflows/android-build-paper.yml

@@ -0,0 +1,35 @@
+name: Test Android build (Paper)
+on:
+  pull_request:
+    paths:
+      - '.github/workflows/android-build-paper.yml'
+      - 'packages/react-native-gesture-handler/android/**'
+  push:
+    branches:
+      - main
+  workflow_dispatch:
+jobs:
+  build:
+    if: github.repository == 'software-mansion/react-native-gesture-handler'
+    runs-on: ubuntu-latest
+    env:
+      WORKING_DIRECTORY: 'apps/ExpoExample'
+    steps:
+      - name: checkout
+        uses: actions/checkout@v4
+      - name: Use Java 17
+        uses: actions/setup-java@v4
+        with:
+          distribution: 'oracle'
+          java-version: '17'
+      - name: Use Node.js 18
+        uses: actions/setup-node@v4
+        with:
+          node-version: 18
+          cache: 'yarn'
+      - name: Install node dependencies
+        working-directory: ${{ env.WORKING_DIRECTORY }}
+        run: PAPER_ENABLED=1 yarn install --immutable
+      - name: Build app
+        working-directory: ${{ env.WORKING_DIRECTORY }}/android
+        run: ./gradlew assembleDebug --console=plain -PreactNativeArchitectures=arm64-v8a

.github/workflows/check-archs-consistency.yml

@@ -30,4 +30,4 @@ jobs:
       - name: Install node dependencies
         run: yarn
       - name: Check Android Paper & Fabric generated interfaces consistency
-        run: yarn architectures-consistency-check
+        run: yarn workspace react-native-gesture-handler architectures-consistency-check

.github/workflows/ios-build-paper.yml

@@ -0,0 +1,35 @@
+name: Test iOS build (paper)
+on:
+  pull_request:
+    paths:
+      - '.github/workflows/ios-build-paper.yml'
+      - 'packages/react-native-gesture-handler/RNGestureHandler.podspec'
+      - 'packages/react-native-gesture-handler/apple/**'
+  push:
+    branches:
+      - main
+  workflow_dispatch:
+jobs:
+  build:
+    if: github.repository == 'software-mansion/react-native-gesture-handler'
+    runs-on: macos-14
+    env:
+      WORKING_DIRECTORY: 'apps/ExpoExample'
+    steps:
+      - name: checkout
+        uses: actions/checkout@v4
+      - name: Use latest stable Xcode
+        uses: maxim-lobanov/setup-xcode@v1
+        with:
+          xcode-version: '16.1'
+      - name: Use Node.js 18
+        uses: actions/setup-node@v4
+        with:
+          node-version: 18
+          cache: 'yarn'
+      - name: Install node dependencies
+        working-directory: ${{ env.WORKING_DIRECTORY }}
+        run: PAPER_ENABLED=1 yarn install --immutable
+      - name: Build app
+        working-directory: ${{ env.WORKING_DIRECTORY }}
+        run: npx react-native run-ios

.github/workflows/static-root-checks.yml

@@ -35,4 +35,4 @@ jobs:
         run: yarn lint-js
       - name: Check for circular dependencies
         working-directory: ${{ env.WORKING_DIRECTORY }}
-        run: yarn circular-dependency-check
+        run: yarn workspace react-native-gesture-handler circular-dependency-check

apps/ExpoExample/app.config.js

@@ -0,0 +1,53 @@
+const shouldEnablePaper = process.env.PAPER_ENABLED === '1';
+
+export default {
+  expo: {
+    name: 'ExpoExample',
+    slug: 'ExpoExample',
+    version: '1.0.0',
+    orientation: 'portrait',
+    icon: './assets/icon.png',
+    userInterfaceStyle: 'light',
+    newArchEnabled: !shouldEnablePaper,
+    splash: {
+      image: './assets/splash.png',
+      resizeMode: 'cover',
+      backgroundColor: '#F8F9FF',
+    },
+    ios: {
+      supportsTablet: true,
+      bundleIdentifier: 'com.example.ExpoExample',
+      buildNumber: '1',
+    },
+    android: {
+      versionCode: 1,
+      adaptiveIcon: {
+        foregroundImage: './assets/adaptive-icon.png',
+        backgroundColor: '#F8F9FF',
+      },
+      edgeToEdgeEnabled: true,
+      package: 'com.example.ExpoExample',
+    },
+    web: {
+      favicon: './assets/favicon.png',
+    },
+    plugins: [
+      [
+        'expo-camera',
+        {
+          cameraPermission: 'Allow RNGH example to access your camera',
+        },
+      ],
+      [
+        'expo-font',
+        {
+          fonts: [
+            './node_modules/@swmansion/icons/fonts/broken/swm-icons-broken.ttf',
+            './node_modules/@swmansion/icons/fonts/outline/swm-icons-outline.ttf',
+            './node_modules/@swmansion/icons/fonts/curved/swm-icons-curved.ttf',
+          ],
+        },
+      ],
+    ],
+  },
+};