fix: fix readme according to prisma update (#40)

zillding · web-flow · commit 6055ebc6ac9d · 2021-12-16T19:37:24.000+08:00
diff --git a/README.md b/README.md
@@ -19,6 +19,7 @@ Based on [Officially Supported Databases](https://www.prisma.io/docs/), the curr
 - PostgreSQL
 - MySQL
 - SQLite
+- MongoDB (Preview)
 
 You may find other 3rd-party supported DBs in Prisma website or other places.
 
