docs: add plugin setup guide

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

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+#pragma once
+
+namespace RE
+{
+	template <class T, std::uintptr_t MASK = 1>
+	class BSTPointerAndFlags
+	{
+	public:
+		using value_type = T;
+		using element_type = typename T::element_type;
+
+		constexpr BSTPointerAndFlags() noexcept = default;
+
+		BSTPointerAndFlags(const BSTPointerAndFlags& a_rhs) { _storage.ptr = a_rhs.get(); }
+
+		constexpr BSTPointerAndFlags(BSTPointerAndFlags&& a_rhs) noexcept
+		{
+			_storage.address = a_rhs._storage.address;
+			a_rhs._storage.address = 0;
+		}
+
+		constexpr BSTPointerAndFlags(std::nullptr_t) noexcept {}
+
+		~BSTPointerAndFlags()
+		{
+			clear_flags();
+			_storage.ptr.~value_type();
+			_storage.address = 0;
+		}
+
+		BSTPointerAndFlags& operator=(const BSTPointerAndFlags& a_rhs)
+		{
+			if (this != std::addressof(a_rhs)) {
+				clear_flags();
+				_storage.ptr = a_rhs.get();
+			}
+			return *this;
+		}
+
+		BSTPointerAndFlags& operator=(BSTPointerAndFlags&& a_rhs) noexcept
+		{
+			if (this != std::addressof(a_rhs)) {
+				clear_flags();
+				a_rhs.clear_flags();
+				_storage.address = a_rhs._storage.address;
+				a_rhs._storage.address = 0;
+			}
+			return *this;
+		}
+
+		void reset() noexcept
+		{
+			clear_flags();
+			_storage.ptr.reset();
+		}
+
+		[[nodiscard]] element_type* get() const noexcept
+		{
+			auto ptr = _storage.address;
+			return reinterpret_cast<element_type*>(ptr & ~FLAG_MASK);
+		}
+
+		[[nodiscard]] element_type& operator*() const noexcept
+		{
+			assert(get() != nullptr);
+			return *get();
+		}
+
+		[[nodiscard]] element_type* operator->() const noexcept { return get(); }
+
+		[[nodiscard]] explicit operator bool() const noexcept { return get() != nullptr; }
+
+	protected:
+		union Storage
+		{
+			~Storage() noexcept {}
+
+			value_type     ptr;
+			std::uintptr_t address{ 0 };
+		};
+
+		constexpr void clear_flags() noexcept { _storage.address &= ~FLAG_MASK; }
+
+		static constexpr std::uintptr_t FLAG_MASK = MASK;
+
+		// members
+		Storage _storage;  // 0
+	};
+}