docs: add plugin setup guide

plugin/lib/commonlibf4/include/RE/D/DECAL_DATA_DATA.h

@@ -0,0 +1,21 @@
+#pragma once
+
+namespace RE
+{
+	class DECAL_DATA_DATA
+	{
+	public:
+		// members
+		float         decalMinWidth;   // 00
+		float         decalMaxWidth;   // 04
+		float         decalMinHeight;  // 08
+		float         decalMaxHeight;  // 0C
+		float         depth;           // 10
+		float         shininess;       // 14
+		float         parallaxScale;   // 18
+		std::int8_t   parallaxPasses;  // 1C
+		std::int8_t   flags;           // 1D
+		std::uint32_t color;           // 20
+	};
+	static_assert(sizeof(DECAL_DATA_DATA) == 0x24);
+}