docs: add plugin setup guide

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

@@ -0,0 +1,14 @@
+#pragma once
+
+namespace RE
+{
+	class BGSEquipIndex
+	{
+	public:
+		~BGSEquipIndex() noexcept {}  // NOLINT(modernize-use-equals-default)
+
+		// members
+		std::uint32_t index;  // 0
+	};
+	static_assert(sizeof(BGSEquipIndex) == 0x4);
+}