Add disclaimer to snowflake db driver

Author: dhui

database/snowflake/README.md

@@ -7,4 +7,6 @@
 | `x-migrations-table` | `MigrationsTable` | Name of the migrations table |
 
 Snowflake is PostgreSQL compatible but has some specific features (or lack thereof) that require slightly different behavior.
-Snowflake doesn't run locally hence there are no tests. The library works against hosted instances of snowflake.
+
+## Status
+This driver is not officially supported as there are no tests for it.