[Proto] Create icon sets in project proto

proto/src/main/proto/project.proto

@@ -14,6 +14,7 @@ message Project {
   repeated WidgetAsset widgets = 8;
   repeated AnimationAsset animations = 9;
   repeated SoundAsset sounds = 10;
+  repeated IconSetAsset iconSets = 11;
 }
 
 message GameMapAsset {
@@ -68,4 +69,12 @@ message SoundAsset {
   required string uid = 1;
   required string source = 2;
   required string name = 3;
+}
+
+message IconSetAsset {
+  required string uid = 1;
+  required string source = 2;
+  required string name = 3;
+  required uint32 rows = 4;
+  required uint32 columns = 5;
 }