Add server start instruction

[efojs]

After initial installation server was up and running.
But after restarting computer (or something, not sure) could not connect:

$ redis-cli 
Could not connect to Redis at 127.0.0.1:6379: Connection refused
not connected>

Spent some time understanding how I started it initially (still not sure).

Having found answer how to start it on askubuntu.com, googled if Redis docs have this instruction (site:redis.io "service redis-server" start) — found it on Windows page

[netlify]

👷 Deploy request for redis-doc pending review.

Visit the deploys page to approve it

Name	Link
🔨 Latest commit	2679e5f

[CLAassistant]

All committers have signed the CLA.