feat(confirm): add `--show-output`

[vahnrr]

Fixes nothing, this is a feature I found missing from a specific use case I had in mind.

Changes

Adds the --show-output flag to gum confirm which prints the prompt and the chosen action to STDOUT.

gum confirm --show-output 'Do you agree?'
# Do you agree? Yes

gum confirm --show-output 'Do you agree?'
# Do you agree? No
# exit status 1

This merge adds 2 commits, only the first one (4f9235b) is required for the feature to work. Since the feature doesn't affect confirm/confirm.go I feel like the second (432182f) isn't necessary, but I still included it in case I misunderstood the purpose of the model structure.