docs: add plugin setup guide

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

@@ -0,0 +1,12 @@
+#pragma once
+
+namespace RE
+{
+	class BSEventFlag
+	{
+	public:
+		// members
+		void* event{ nullptr };  // 0
+	};
+	static_assert(sizeof(BSEventFlag) == 0x8);
+}