feat: Add an option to listen to the start conversation click events (#8038)

This PR will add a new event chatwoot:on-start-conversation to the chat widget, which you can listen to and trigger custom interactions on your end.

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

app/views/widget_tests/index.html.erb

@@ -59,4 +59,9 @@ window.addEventListener('chatwoot:error', function(e) {
 window.addEventListener('chatwoot:on-message', function(e) {
   console.log('chatwoot:on-message', e.detail)
 })
+
+
+window.addEventListener('chatwoot:on-start-conversation', function(e) {
+  console.log('chatwoot:on-start-conversation')
+})
 </script>