Update the README to use the steam apt repository

[Pandapip1]

Also worth noting: the program / OS versions being referenced are ancient.

[TTimo]

The direct link to the .deb installer works here (http://media.steampowered.com/client/installer/steam.deb)

Using the apt is a perfectly valid way to get setup of course, but we don't really push it to users as it's more steps, more complexity and not strictly necessary.

[Pandapip1]

Using the apt is a perfectly valid way to get setup of course, but we don't really push it to users as it's more steps, more complexity and not strictly necessary.

As someone that strongly prefers to use apt where possible, would it increase the chances of this PR getting approved for me to write a short script that can be curl <url> | sudo sh'd?