Add to readme: do not use root

[kroggen]

Add to somewhere on the readme that installation as root is not supported

[yufansong]

What do you mean installation as root is not supported ? You mean agent cannot run as root in sandbox or you cannot install opendevin as root? Can you elaborate more details?

[rbren]

Going to close this one--not entirely clear what the issue is, and hopefully docker run makes it easier

[kroggen]

It is not possible to run OpenDevin as root.

Check #969 and #887