feat: Add support for dark mode in dashboard (#7460)

- Add config for TailwindCSS
- Enable HMR
- Add a config in LocalStorage for Dark Mode

Co-authored-by: Pranav Raj S <pranav@chatwoot.com>

app/javascript/dashboard/assets/scss/_helper-classes.scss

@@ -1,5 +1,5 @@
 .bg-light {
-  @include background-light;
+  @apply bg-slate-25 dark:bg-slate-800;
 }
 
 .flex-center {