docs: add plugin setup guide

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

@@ -0,0 +1,16 @@
+#pragma once
+
+namespace RE
+{
+	namespace PerkAdded
+	{
+		class Event
+		{
+		public:
+			const Actor*   adder;
+			const BGSPerk* perk;
+			std::uint8_t   rank;
+		};
+		static_assert(sizeof(Event) == 0x18);
+	}
+}