ncls: scale modes "scaleup" and "scaledown"

[tomek-szczesny]

Hey Nick, it's been a while!

I'm currently using ncls for plotting some pictures in kitty, of varying size (dot graphs). It's a shell script.

The trouble is, I cannot predict how big of a picture (or terminal) I'll be dealing with, and apparently there is no single scale mode that can show the picture in original size if it fits, and scale it down to fit otherwise.

Hence I propose adding two new modes, that scale up or down only.

I know I could do a hack to determine picture size beforehand and adjust scaling accordingly, but I'm speaking for those who cannot do it on their own. :)

I also propose to make "scaledown" the default option. Running ncls in a directory full of icons is currently .. less than ideal. :)