refactor(ng-dev/commit-message): add more deprecation format (#2627)

This will give more info on the correct deprecation notice expected in the commit body

PR Close #2627

Author: JeanMeche

ng-dev/commit-message/validate.ts

@@ -228,5 +228,9 @@ export function printValidationErrors(errors: string[], print = Log.error) {
   print();
   print(`<breaking change description>`);
   print();
+  print(`DEPRECATED: <deprecation summary>`);
+  print();
+  print(`<deprecation description>`);
+  print();
   print();
 }