woopsie, fix typo

react-native-webview.podspec

 Pod::Spec.new do |s|
   s.name         = package['name']
   s.version      = package['version']
-  s.summary      = package['description]
+  s.summary      = package['description']
 
   s.authors      = package['author']
   s.homepage     = package['homepage']