add omitempty config to example gqlgen.yml (#2880)

Co-authored-by: Pavel Vasilenka <pvasilenka@mobalyticshq.com>

_examples/uuid/gqlgen.yml

@@ -57,6 +57,9 @@ resolver:
 # Optional: wrap nullable input fields with Omittable
 # nullable_input_omittable: true
 
+# Optional: turn on `json:",omitempty"` tags on model types, default true
+# enable_model_json_omitempty_tag: true
+
 # Optional: set to speed up generation time by not performing a final validation pass.
 # skip_validation: true