Add @JeromeJu as a pipelines maintainer

Jerome has been consistently contributing to pipelines for a long while now. He drove much of the long and complicated v1 CRD migration in addition to his recent work around feature flags and software versioning. Along the way, he has racked up well over a 100+ reviews:

https://github.com/tektoncd/pipeline/pulls?q=is%3Apr++reviewed-by%3AJeromeJu+-author%3AJeromeJu+

OWNERS_ALIASES

@@ -12,6 +12,7 @@ aliases:
   - wlynch
   - yongxuanzhang
   - chitrangpatel
+  - jeromeJu
 
   pipeline-reviewers:
   - afrittoli