Added french translation files for backend and frontend.

backend/fr/conversations.json

@@ -0,0 +1,8 @@
+{
+    "tlConversations": {
+        "start_conversation": "Start conversation",
+        "view_conversation": "View conversation",
+        "conversations": "Conversations",
+        "no_messages": "There are no messages here."
+    }
+}