[DOC] Fix typo, add DATABASE_URL export command.
[DOC] Fix typo, add DATABASE_URL export command.

Parkjeahwan/awegeeks,Parkjeahwan/awegeeks,zealord/gatewayd,crazyquark/gatewayd,xdv/gatewayd,zealord/gatewayd,crazyquark/gatewayd,whotooktwarden/gatewayd,whotooktwarden/gatewayd,xdv/gatewayd