docs: add plugin setup guide

plugin/lib/commonlibf4/include/RE/B/BGSDecalEmitter.h

@@ -0,0 +1,20 @@
+#pragma once
+
+#include "RE/N/NiPointer.h"
+
+namespace RE
+{
+	class BGSImpactData;
+	class BSTempEffectParticle;
+
+	class BGSDecalEmitter
+	{
+	public:
+		// members
+		std::int32_t                    decalsToEmit;     // 00
+		bool                            finished;         // 04
+		BGSImpactData*                  decalImpactData;  // 08
+		NiPointer<BSTempEffectParticle> particleData;     // 10
+	};
+	static_assert(sizeof(BGSDecalEmitter) == 0x18);
+}