Keyboard keys for not going past end of a slide

[christuart]

When presenting, I want to be able to press and hold or repeatedly press a control to get past the last stop point on a slide, without accidentally going to the next slide.

I therefore want a control that moves past stop points but doesn't move to the next slide.

I propose next line controls which should do this to be j, down arrow and space. The other next slide controls would continue to behave as they currently do.

[visit1985]

Thanks for your contribution @christuart. I gave it a try, and I think this would confuse quite some people, as this is not how this keys usually work. :man_shrugging:

It could be less distractive to be able to go back to the last slide without having to skip through all the stop points again. What do you think? We could remove this (or make it configurable): https://github.com/visit1985/mdp/blob/4349c96187dcf97eedcbe7297379df42f705757e/src/viewer.c#L409-L411