feat: Update the design for the Inbox management console (#10043)

This is the continuation of the design update PR. This changes the design for the inbox pages.
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Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>
Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>

app/javascript/dashboard/helper/featureHelper.js

@@ -9,6 +9,7 @@ const FEATURE_HELP_URLS = {
   custom_attributes: 'https://chwt.app/hc/custom-attributes',
   dashboard_apps: 'https://chwt.app/hc/dashboard-apps',
   help_center: 'https://chwt.app/hc/help-center',
+  inboxes: 'https://chwt.app/hc/inboxes',
   integrations: 'https://chwt.app/hc/integrations',
   labels: 'https://chwt.app/hc/labels',
   macros: 'https://chwt.app/hc/macros',