docs: add plugin setup guide

plugin/lib/commonlibf4/include/Scaleform/G/GFx_ExternalLibPtr.h

@@ -0,0 +1,20 @@
+#pragma once
+
+namespace Scaleform::GFx
+{
+	class MovieImpl;
+
+	class __declspec(novtable) ExternalLibPtr
+	{
+	public:
+		ExternalLibPtr(MovieImpl* a_movieRoot) :
+			owner(a_movieRoot)
+		{}
+
+		virtual ~ExternalLibPtr() = default;
+
+		// members
+		MovieImpl* owner;
+	};
+	static_assert(sizeof(ExternalLibPtr) == 0x10);
+}