Add PostgreSQL support via pg and node-postgres drizzle adapter

.env.example

@@ -8,6 +8,7 @@
 # directly (drizzle-kit, scripts). Keep both in step and keep them well below
 # MariaDB's `max_connections` (151 by default) or the emulator and any second
 # CMS instance get "Too many connections". README §performance: pool size 25.
+# DATABASE_URL supports both MySQL/MariaDB ("mysql://...") and PostgreSQL ("postgres://...").
 DATABASE_URL="mysql://user:password@localhost:3306/dbname?charset=utf8mb4&connection_limit=25&connect_timeout=5"
 DATABASE_POOL_SIZE=25
 DATABASE_IDLE_TIMEOUT_MS=60000