Make ouch accessible

[AntonHermann]

The warnings and info messages are not accessible at the moment, the square brackets are most likely read out as square brackets and I'm not sure whether having a message for each (de)compressed file is valuable for a sight-impaired person.

Motivation
See this blogpost for some arguments/guidelines for making hacking accessible (there are many CLI specific informations)

What should change?
Not much actually, I think adding an accessibility option and disabling all info! output as well as removing the square brackets for warning! output and checking all (e)print(ln)!s whether they provide value to a sight-impaired person.

Implementation ideas
I don't know whether it would be too much clutter to pass this option to every output macro call, so here are some ideas how this could be implemented in a less noise way:

• Pass it to every output macro, but extract this and other flags into a new struct that can be passed around comfortably (the subset of opts::Opts that can be Copyed)
• Use an env var instead which can be checked in the output macros
• global state (using once_cell)

This could be advertised as a feature in the readme. Many CLI tools are not designed with accessibility in mind. We could make a difference towards making CLI more accessible in general and thus including an often forgotten minority! 🎉

[AntonHermann]

whops didn't know it would at the documentation label, that shouldn't be there