add clickhouse to onprem database

Signed-off-by: Slach <bloodjazman@gmail.com>

diagrams/onprem/database.py

@@ -11,6 +11,8 @@ class _Database(_OnPrem):
 class Cassandra(_Database):
     _icon = "cassandra.png"
 
+class Clickhouse(_Database):
+    _icon = "clickhouse.png"
 
 class Cockroachdb(_Database):
     _icon = "cockroachdb.png"