Add vterm-ignore-cursor-change

[Azkae]

Add an option to ignore application request to modify cursor shape or visibility.

I use meow, which uses cursor shape to differentiate between normal and insert mode, so I prefer if the application cannot change the cursor shape.

[fredericgiquel]

This MR is useful for evil too, particularly with version 4.0 of fish shell which regularly changes the cursor shape.

The patch is small. I tested it and it seems to work well.
Is there anything preventing the merge ?