docs: add plugin setup guide

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

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+#pragma once
+
+namespace RE
+{
+	// maps a key to a uint32_t index
+	// the value of the index is provided externally (typically just some counter)
+	// this index is used to index an array, which is also provided externally
+	// essentially implements a scatter table with chaining for conflict resolution
+	// it is honestly impressive how awful this data structure is, bethesda never fails to impress
+	template <class Traits, class Accessor>
+	class BSTSmallIndexScatterTable
+	{
+	public:
+		struct entry_type
+		{
+			std::uint16_t next = 0xFFFF;   // the next slot the check for conflict resolution, or 0xFFFF if no chain
+			std::uint16_t index = 0xFFFF;  // the actual index, or 0xFFFF if invalid
+		};
+
+		std::uint64_t pad;       // 00
+		entry_type*   table;     // 08
+		std::uint32_t size;      // 10
+		std::uint32_t mask;      // 14
+		std::uint32_t avail;     // 18
+		std::uint32_t lastFree;  // 1C
+	};
+	// static_assert(sizeof(BSTSmallIndexScatterTable) == 0x20);
+}