LibWeb/WebGL: Implement WEBGL_draw_buffers extension

Author: https://github.com/Lubrsi
Commit: 55f7cb4f10
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/3239
Reviewed-by: https://github.com/awesomekling
Reviewed-by: https://github.com/kalenikaliaksandr

Libraries/LibWeb/WebGL/WebGLRenderingContext.h

@@ -83,6 +83,7 @@ private:
     // "Multiple calls to getExtension with the same extension string, taking into account case-insensitive comparison, must return the same object as long as the extension is enabled."
     GC::Ptr<Extensions::ANGLEInstancedArrays> m_angle_instanced_arrays_extension;
     GC::Ptr<Extensions::OESVertexArrayObject> m_oes_vertex_array_object_extension;
+    GC::Ptr<Extensions::WebGLDrawBuffers> m_webgl_draw_buffers_extension;
 
     virtual void set_error(GLenum error) override;
 };