Chore: moves localstorage helper as a shared utility (#6838)

* Chore: moves localstorage helper as a shared utility and refactors constants

* Refactors constants file

* Fixes merge conflicts

* Delete constants.js

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Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>

app/javascript/dashboard/constants/localStorage.js

@@ -0,0 +1,5 @@
+export const LOCAL_STORAGE_KEYS = {
+  DISMISSED_UPDATES: 'dismissedUpdates',
+  WIDGET_BUILDER: 'widgetBubble_',
+  DRAFT_MESSAGES: 'draftMessages',
+};