docs: add plugin setup guide

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

@@ -0,0 +1,71 @@
+#pragma once
+
+namespace RE
+{
+	namespace BSBTreeFile
+	{
+		template <class Key, std::size_t PAGE_SIZE>
+		class PageBasics
+		{
+		public:
+			using key_type = Key;
+
+			class InteriorNode;
+		};
+
+		template <class T, class Key, std::size_t PAGE_SIZE>
+		class PGFSEDL :
+			public PageBasics<Key, PAGE_SIZE>
+		{
+		public:
+			using key_type = Key;
+
+			class LeafNode;
+		};
+
+		template <class Pager, class Impl, std::size_t MAX_DEPTH>
+		class BPTree :
+			public Impl  // 00
+		{
+		public:
+			class PagePtr
+			{
+			public:
+				// members
+				union
+				{
+					typename Impl::InteriorNode* interior;
+					typename Impl::LeafNode*     leaf;
+					void*                        ptr = nullptr;
+				};  // 0
+			};
+			// static_assert(sizeof(PagePtr) == 0x8);
+
+			class Cursor
+			{
+			public:
+				class PageEntry
+				{
+				public:
+					// members
+					PagePtr       page = {};      // 00
+					std::uint64_t pageIndex = 0;  // 08
+				};
+				// static_assert(sizeof(PageEntry) == 0x10);
+
+				// members
+				PageEntry     pages[MAX_DEPTH] = {};      // 00
+				std::uint32_t positions[MAX_DEPTH] = {};  // ??
+				std::uint32_t depth = 0;                  // ??
+			};
+
+			// members
+			Pager*        fpol = nullptr;     // 00
+			PagePtr*      root = nullptr;     // 18
+			std::uint64_t rootPageIndex = 0;  // 10
+			std::uint32_t active = 0;         // 18
+			std::uint32_t depth = 0;          // 1C
+		};
+		// static_assert(sizeof(BPTree) == 0x20);
+	}
+}