Issue type:

[ ] question
[ ] bug report
[x] feature request
[ ] documentation issue

Database system/driver:

[ ] cordova
[x] mongodb
[ ] mssql
[ ] mysql / mariadb
[ ] oracle
[ ] postgres
[ ] cockroachdb
[ ] sqlite
[ ] sqljs
[ ] react-native
[ ] expo

TypeORM version:

[x] latest
[ ] @next
[ ] 0.x.x (or put your version here)

Steps to reproduce or a small repository showing the problem:
There is no necessary steps to reproduce warning. Just create any database connection using sample mongodb and it will come back.

(node:9868) DeprecationWarning: current Server Discovery and Monitoring engine is deprecated, and will be removed in a future version. To
use the new Server Discover and Monitoring engine, pass option { useUnifiedTopology: true } to MongoClient.connect.