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/_utility-helpers.scss

@@ -43,17 +43,13 @@
 }
 
 .border-right {
-  border-right: 1px solid var(--color-border);
+  @apply border-r border-slate-50 dark:border-slate-700;
 }
 
 .border-left {
   border-left: 1px solid var(--color-border);
 }
 
-.bg-white {
-  background-color: var(--white);
-}
-
 .text-ellipsis {
   overflow: hidden;
   text-overflow: ellipsis;