Ability to customize the keybindings that are recognized while editing a cell value

[ei14]

In visidata/_input.py on line 607, the cell-edit keybindings are hardcoded. It would be nice if we could customize these values in a config file.

My motivating example: I do a lot of manual data entry, so when I'm finished typing the value in a particular row, I want to quickly move to the next row. The shortcut to do this is Shift+Down, but this requires moving my hand from the numbers to the arrow keys; for a lot of data entry, this time wastage adds up fast! I want Ctrl+N and Ctrl-P to mean "next line" and "previous line" respectively, as these are much faster to type. I actually achieved this by modifying the source code and recompiling, but it would be nice if I didn't have to resort to such measures.

Thanks in advance! I'm really impressed by visidata; I only first heard of it a few hours ago. Wonderful software!