redoc-cli bundle fails if output path does not exist

[brushmate]

CLI fails with the following message if a non-existing path is given to the --output option:

$ npx redoc-cli bundle --output ./non/existing/path/index.html spec.yaml 
Prerendering docs
ENOENT: no such file or directory, open './non/existing/path/index.html'

It would be nice if the directories would be created automatically.

[RomanHotsiy]

A good opportunity for a PR 😄

[brushmate]

Sure :D I am already working on it but also wanted to document it in an issue.