LibGfx: Add Matrix4x4::elements() getters

Author: https://github.com/alimpfard
Commit: https://github.com/SerenityOS/serenity/commit/2d96437bbb5
Pull-request: https://github.com/SerenityOS/serenity/pull/2869
Reviewed-by: https://github.com/awesomekling

Libraries/LibGfx/Matrix4x4.h

@@ -48,6 +48,9 @@ public:
     {
     }
 
+    auto elements() const { return m_elements; }
+    auto elements() { return m_elements; }
+
     Matrix4x4 operator*(const Matrix4x4& other) const
     {
         Matrix4x4 product;