add docker run instructions to README.md

Summary: Nie ma taska

Test Plan: Przeczytaj README.md

Reviewers: #reviewers, kuba-orlik

Reviewed By: #reviewers, kuba-orlik

Subscribers: kuba-orlik, jenkins-user

Differential Revision: https://hub.sealcode.org/D1090

README.md

@@ -6,6 +6,8 @@ rendered front-end.
 ## Running
 
 ```
+docker-compose up -d db
+
 npm install
 npm run watch
 ```