add 'from the command line' to tutorial-createdb.html

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/16/tutorial-createdb.html
Description:

https://www.postgresql.org/docs/16/tutorial-createdb.html

it says ...

"To create a new database, in this example named mydb, you use the
following command:"

To make it more clear that this is being executed from the cli (and not the
psql console) I suggest to change this to

"To create a new database from the command line, in this example named
mydb, you use the following command:"