LibWeb: Implement <feComposite> SVG filter

Author: https://github.com/tcl3
Commit: a00e7cb20b
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/5744
Reviewed-by: https://github.com/gmta ✅
Reviewed-by: https://github.com/konradekk

Libraries/LibWeb/Forward.h

@@ -1087,6 +1087,7 @@ class SVGDescElement;
 class SVGElement;
 class SVGEllipseElement;
 class SVGFEBlendElement;
+class SVGFECompositeElement;
 class SVGFEFloodElement;
 class SVGFEGaussianBlurElement;
 class SVGFEImageElement;