Extract RN version

Author: testableapple

examples/SampleApp/fastlane/Fastfile

@@ -7,6 +7,7 @@ xcode_project = 'ios/SampleApp.xcodeproj'
 xcode_workspace = 'ios/SampleApp.xcworkspace'
 template_app_name = 'DemoApp'
 bundletool_version = '1.17.1'
+react_native_version = '0.74.5'
 @force_check = false
 temp_dir = Dir.mktmpdir
 
@@ -213,9 +214,7 @@ end
 lane :frameworks_sizes do
   rn_project_dir = create_template_project
 
-  Dir.chdir(rn_project_dir) do
-    sh('yarn add react-native@0.74.5')
-  end
+  Dir.chdir(rn_project_dir) { sh("yarn add react-native@#{react_native_version}") }
 
   android_app_size_without_sdk = android_app_size(rn_project_dir: rn_project_dir)
   ios_app_size_without_sdk = ios_app_size(rn_project_dir: rn_project_dir)