Use the current layout instead of the us layout

[ngn13]

• This fix issue: none

PR Description:

By default, the installer selects the "us" layout. With this simple enhancement, it selects the current layout (acquired by parsing localectl status output) instead of "us".

So if the user runs loadkeys or localectl set-keymap before running archinstall, they won't have to set their keymap again.

Tests and Checks

• I have tested the code! (on my local machine, there is no link to the ISO)
  

[Torxed]

Looks good to me, and I don't see a reason for not setting the default to whatever the user has provided before launching archinstall.

[svartkanin]

looks good thanks for that!