docs: add plugin setup guide

plugin/lib/commonlibf4/include/RE/P/PlayerCrosshairModeEvent.h

@@ -0,0 +1,24 @@
+#pragma once
+
+namespace RE
+{
+	enum class CrosshairMode;
+
+	class PlayerCrosshairModeEvent :
+		public BSTValueEvent<CrosshairMode>
+	{
+	private:
+		using EventSource_t = BSTGlobalEvent::EventSource<PlayerCrosshairModeEvent>;
+
+	public:
+		[[nodiscard]] static EventSource_t* GetEventSource()
+		{
+			static REL::Relocation<EventSource_t**> singleton{ ID::PlayerCrosshairModeEvent::GetEventSource };
+			if (!*singleton) {
+				*singleton = new EventSource_t(&BSTGlobalEvent::GetSingleton()->eventSourceSDMKiller);
+			}
+			return *singleton;
+		}
+	};
+	static_assert(sizeof(PlayerCrosshairModeEvent) == 0x08);
+}