Add View option to see the diff in context of the whole file

### What do you want to change?

Thanks for doing `hunk`! It's very nice, for isolated-diff viewing.

I'm used to using `meld` which shows the diffs in context of the whole file, but it's a separate app whose window behaves oddly in macOS.

### Why?

I find this lets me see the surrounding context, which helps a lot in reviewing diffs.

### How? (optional)

_No response_