LibWeb/CSP: Implement the script-src-attr directive

Author: https://github.com/Lubrsi
Commit: f50f23b19f
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/5404
Reviewed-by: https://github.com/shannonbooth ✅

Libraries/LibWeb/Forward.h

@@ -140,6 +140,7 @@ class ImageSourceDirective;
 class ManifestSourceDirective;
 class MediaSourceDirective;
 class ObjectSourceDirective;
+class ScriptSourceAttributeDirective;
 class ScriptSourceDirective;
 class ScriptSourceElementDirective;
 struct SerializedDirective;