Added validation for command triggers (#3068)

webapp/utils/constants.jsx

@@ -644,6 +644,8 @@ export default {
     MAX_USERNAME_LENGTH: 22,
     MIN_PASSWORD_LENGTH: 5,
     MAX_PASSWORD_LENGTH: 50,
+    MIN_TRIGGER_LENGTH: 1,
+    MAX_TRIGGER_LENGTH: 128,
     TIME_SINCE_UPDATE_INTERVAL: 30000,
     MIN_HASHTAG_LINK_LENGTH: 3,
     EMOJI_PATH: '/static/emoji',