chore(ui): nicer threshold prompt

[David-Kunz]

Hi Folke,

Great plugin! Here's a little change to the prompt:

From

to

Note: The default value is already set in the beginning. The original prompt didn't make it clear, that 0 is the default and 0.5 is an example.

[folke]

I uses dressgin.nvim, so for me it was fine, but this is better. Thank you!