WIP: Fit more of the list of available numbers on screen

register1 lists all available numbers in an area code, at least all that your telco has (btw it might help to clarify that with some copytext). There can be a lot of them and choosing between them can be hard, though it's good that the option is there.

This commit reflows the the list using the new column-count feature. On small screens this should display much like the list it is now; on large screens it should show 3 columns side-by-side.

{ insert screenshot here :P }

The only way I knew how to do this was with <li>s, so that's what is here, though column-count applies to any HTML: https://www.w3schools.com/css/tryit.asp?filename=trycss3_column-count; I don't know if there's a way in HTML5+CSS3 to reflow a full table (including reflowing the headers) but I suspect there is;