LibWeb/CSP: Implement the style-src-elem directive

Author: https://github.com/Lubrsi
Commit: 574b736156
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/5490
Reviewed-by: https://github.com/shannonbooth ✅

Libraries/LibWeb/CMakeLists.txt

@@ -61,6 +61,7 @@ set(SOURCES
     ContentSecurityPolicy/Directives/SerializedDirective.cpp
     ContentSecurityPolicy/Directives/SourceExpression.cpp
     ContentSecurityPolicy/Directives/StyleSourceDirective.cpp
+    ContentSecurityPolicy/Directives/StyleSourceElementDirective.cpp
     ContentSecurityPolicy/Policy.cpp
     ContentSecurityPolicy/PolicyList.cpp
     ContentSecurityPolicy/SecurityPolicyViolationEvent.cpp