fix(ios): prevent tree shaking by including dummy function

Signed-off-by: Amogh Lele <amolele@gmail.com>

ios/readability.podspec

@@ -22,6 +22,9 @@ A new Flutter FFI plugin project.
   s.dependency 'Flutter'
   s.platform = :ios, '12.0'
 
+  s.public_header_files = 'Classes/**/*.h'
+  s.vendored_frameworks = 'libreadability.xcframework'
+
   # Flutter.framework does not contain a i386 slice.
   s.pod_target_xcconfig = { 'DEFINES_MODULE' => 'YES', 'EXCLUDED_ARCHS[sdk=iphonesimulator*]' => 'i386' }
   s.swift_version = '5.0'