fix: fix database path in .env.sample for dev demo setup

Author: yaroslav8765

dev-demo/.env.sample

@@ -7,5 +7,5 @@ HEAVY_DEBUG=
 HEAVY_DEBUG_QUERY=
 PORT=3000
 
-DATABASE_FILE=./db.sqlite
+DATABASE_FILE=./.db.sqlite
 DATABASE_FILE_URL=file:${DATABASE_FILE}