Fix rendering for multi-line commands

[lutzky]

Heredocs can be used to create multi-line commands, which broke rendering.

Details about heredocs: https://www.docker.com/blog/introduction-to-heredocs-in-dockerfiles/

Before:

After:

(Example is adapted from https://fasterthanli.me/series/building-a-rust-service-with-nix/part-6)

[mark2185]

Check out #399 as well, might prove useful.

[lutzky]

Thanks, I've left a comment on #399: https://github.com/wagoodman/dive/pull/399/files#r1166837287

I believe the run-static-analyses failure is unrelated to my change.

[mark2185]

I believe the run-static-analyses failure is unrelated to my change.

I don't want to be the bearer of bad news, but the project has been inactive for a while.

[lutzky]

Damn ^_^

Oh well, I thought it'd be a useful thing. I've only encountered it as part of
https://fasterthanli.me/series/building-a-rust-service-with-nix/part-6, so I figured I'd fix it as I go 🤷

[wagoodman]

thanks for the enhancement here! (force pushed to rebase)