Actually implement ImGui.Combo

src/ImGui.NET/ImGui.cs

@@ -162,7 +162,12 @@ namespace ImGuiNET
 
         public unsafe static bool Combo(string label, ref int current_item, string[] items)
         {
-            throw new NotImplementedException();
+            return ImGuiNative.igCombo(label, ref current_item, items, items.Length, 5);
+        }
+
+        public unsafe static bool Combo(string label, ref int current_item, string[] items, int heightInItems)
+        {
+            return ImGuiNative.igCombo(label, ref current_item, items, items.Length, heightInItems);
         }
 
         public static bool ColorButton(Vector4 color, bool smallHeight, bool outlineBorder)

src/ImGui.NET/ImGuiNative.cs

@@ -313,7 +313,7 @@ namespace ImGuiNET
         public static extern bool igRadioButton(string label, int* v, int v_button);
         [DllImport(cimguiLib)]
         [return: MarshalAs(UnmanagedType.I1)]
-        public static extern bool igCombo(string label, ref int current_item, char** items, int items_count, int height_in_items);
+        public static extern bool igCombo(string label, ref int current_item, string[] items, int items_count, int height_in_items);
         [DllImport(cimguiLib)]
         [return: MarshalAs(UnmanagedType.I1)]
         public static extern bool igCombo2(string label, ref int current_item, string items_separated_by_zeros, int height_in_items);