Youtube Home/Subs - Set videos per row

Simple userstyle that lets you set how many videos per row you'd like to see on your YT Home/Subs page.

"720p: Videos per row" - These options kick in when the viewport (your browser window) width is at least 1280px.
^{I'm using 720p (i.e. the corresponding height for 1280 in 16:9 ratio) in the description, because that is the more well known number, but in actuality, only the width matters here)}
"1080p: Videos per row" - These kick in when the viewport width is at least 1920px
...and so on.

Why so many separate settings?

So that the number of videos per row, and therefore their size, can be dynamic.
5 videos per row might work for 1080p, but then if you dock the window to half the monitor for example, 5 videos per row is a bit much (the videos get small to fit 5 in)
Of course, there are much better ways to make this more dynamic and responsive, but that involves much more work and is more prone to breaking when YT constantly changes stuff. I might take that challenge on at a later date. We'll see.