docs: add plugin setup guide

plugin/lib/commonlibf4/include/RE/S/ScreenshotHandler.h

@@ -0,0 +1,19 @@
+#pragma once
+
+#include "RE/B/BSInputEventUser.h"
+
+namespace RE
+{
+	class __declspec(novtable) ScreenshotHandler :
+		public BSInputEventUser  // 00
+	{
+	public:
+		static constexpr auto RTTI{ RTTI::ScreenshotHandler };
+		static constexpr auto VTABLE{ VTABLE::ScreenshotHandler };
+
+		// members
+		bool screenshotQueued;       // 10
+		bool multiScreenshotQueued;  // 11
+	};
+	static_assert(sizeof(ScreenshotHandler) == 0x18);
+}