[Feature] Email collect message hooks (#331)

- Add email collect hook on creating conversation
- Merge contact if it already exist

app/javascript/widget/assets/scss/_forms.scss

@@ -9,6 +9,7 @@ $input-height: $space-two * 2;
 
   appearance: none;
   background: $color-white;
+  border: 1px solid $color-border;
   border-radius: $border-radius;
   box-sizing: border-box;
   color: $color-body;