fix: add missing output formats in error message

[wyardley]

• Add missing 'junit' and 'pretty' output formats.
• Use quotes vs. backticks around command name

Note:

• I can revert the change removing the backticks, or, if you prefer, I could bold it, which might look better?
• I don't know if you want output or -output vs outputFormat? The user typically invokes the format using -output, I think.
• Could also make this a data structure and try to DRY it up a little, to make the error self-update?

[wyardley]

@yannh let me know if this looks right to you

[yannh]

Thanks for the patch :heart: !