Welcome page

I've been impressed at how much Nyx users miss. Hell, I've met longtime users that didn't even know you could press left/right for additional pages. They thought Nyx had just one!

To be fair Nyx's discoverability sucks. I've tried to keep the most important information simple so it can be displayed on a single line...

m: menu, p: pause, h: page help, q: quit

But maybe we should show a one-time popup to first time Nyx users that explains how Nyx works. We could then persist a 'shown' flag in their home directory to suppress future popups.