added Heejung Hong (#7711)

Author: mchait18

_projects/tdm-calculator.md

@@ -41,6 +41,13 @@ leadership:
       slack: 'https://hackforla.slack.com/team/U01RDSRT46R'
       github: 'https://github.com/Jane4925'
     picture: https://avatars.githubusercontent.com/Jane4925
+  - name: Heejung Hong
+    github-handle: heejung-hong
+    role: Front End Development Lead
+    links:
+      slack: https://hackforla.slack.com/team/U064M7X48SY
+      github: https://github.com/heejung-hong
+    picture: https://avatars.githubusercontent.com/heejung-hong
 links:
   - name: GitHub
     url: 'https://github.com/hackforla/tdm-calculator'