fix: fallback from potentially missing min_ios_version_supported in podspec (#522)

Author: frw

react-native-ssl-public-key-pinning.podspec

@@ -11,7 +11,7 @@ Pod::Spec.new do |s|
   s.license      = package["license"]
   s.authors      = package["author"]
 
-  s.platforms    = { :ios => min_ios_version_supported }
+  s.platforms    = { :ios => defined?(min_ios_version_supported) ? min_ios_version_supported : '11.0' }
   s.source       = { :git => "https://github.com/frw/react-native-ssl-public-key-pinning.git", :tag => "#{s.version}" }
 
   s.source_files = "ios/**/*.{h,m,mm}"