add new struct definitions

Il2CppInspector.Common/Next/BinaryMetadata/Il2CppMethodSpec.cs

@@ -0,0 +1,14 @@
+using VersionedSerialization.Attributes;
+
+namespace Il2CppInspector.Next.BinaryMetadata;
+
+using MethodIndex = int;
+using GenericInstIndex = int;
+
+[VersionedStruct]
+public partial struct Il2CppMethodSpec
+{
+    public MethodIndex MethodDefinitionIndex;
+    public GenericInstIndex ClassIndexIndex;
+    public GenericInstIndex MethodIndexIndex;
+}