feat: conversation participants (#4145)

Fixes #241
Fixes: chatwoot/product#648

Co-authored-by: Aswin Dev P.S <aswindevps@gmail.com>
Co-authored-by: Nithin David Thomas <1277421+nithindavid@users.noreply.github.com>
Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>
Co-authored-by: Pranav Raj S <pranav@chatwoot.com>

app/javascript/dashboard/store/modules/conversations/index.js

@@ -13,6 +13,8 @@ const state = {
   currentInbox: null,
   selectedChatId: null,
   appliedFilters: [],
+  conversationParticipants: [],
+  conversationLastSeen: null,
 };
 
 // mutations