LibGfx: Add scaffolding for reading ICC tag table

The idea is that we'll have one type for each tag type.
For now, this treats all tag types as unknown, but it puts most
of the infrastructure for reading tags in place.

Userland/Utilities/icc.cpp

@@ -73,5 +73,12 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
         outln("{} trailing bytes after profile data", profile_disk_size - profile->on_disk_size());
     }
 
+    outln("");
+
+    outln("tags:");
+    profile->for_each_tag([](auto tag_signature, auto tag_data) {
+        outln("{}: {}, offset {}, size {}", tag_signature, tag_data->type(), tag_data->offset(), tag_data->size());
+    });
+
     return 0;
 }