Prefix message to clarify what is asking for sudo password

[benmccann]

I was type checking a javascript file and through a roundabout manner it was invoking mkcert. It was quite scary that such a simple operation was asking for my sudo password without any explanation of where it was coming from or why it was needed. For such a sensitive operation I think it would be helpful to provide more details

This PR uses the text:

mkcert will now install certificates into your root certificate store.
Enter your sudo password:

If we wanted something shorter another alternative might be:

[mkcert] sudo password:

But I thought the longer message provided more explanation of why it's asking for your sudo password.