added function to insert data

database.py

@@ -148,3 +148,12 @@ class Data_table(Table):
             ';'
         )
         self.execute(query, val_dict)
+
+def insert(username, timestamp, content):
+    val_dict = {
+        'username': username,
+        'time': timestamp,
+        'content': content
+    }
+    with Data_table() as dt:
+        dt.insert(val_dict)