LibWeb/EME: Add EncryptedMedia allowed allowed feature flag

Author: https://github.com/stelar7
Commit: d65f599f92
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/5665
Reviewed-by: https://github.com/gmta ✅
Reviewed-by: https://github.com/trflynn89

Libraries/LibWeb/DOM/Document.cpp

@@ -4450,6 +4450,7 @@ bool Document::is_allowed_to_use_feature(PolicyControlledFeature feature) const
             return true;
         break;
     case PolicyControlledFeature::FocusWithoutUserActivation:
+    case PolicyControlledFeature::EncryptedMedia:
         // FIXME: Implement allowlist for this.
         return true;
     }

Libraries/LibWeb/DOM/Document.h

@@ -158,6 +158,7 @@ struct ElementCreationOptions {
 
 enum class PolicyControlledFeature : u8 {
     Autoplay,
+    EncryptedMedia,
     FocusWithoutUserActivation,
 };