Update trust-cert.sh prompt to use y/n + ENTER

[waldekmastykarz]

Let's update trust-cert.sh to use y/n + ENTER rather than just y/n.

@waldekmastykarz
I come to think how a prompt confirmation Y/n should be completed. It could be either by pressing Enter key or just single key (like 'y'or 'n'). It appears this PR implements key + Enter but trust-cert.sh we run to install a certificate uses single key.
In favor of consistency both have to be the same (I see one more fix comming). But which approach to choose?

The single key is faster, but Key+Enter method sort of safer, gives a better user control and seems to provide adherence to common CLI conventions. So I'd stick with key+enter. What do you think?

Originally posted by @bartizan in #1208 (comment)

[bartizan]

working on it. There is a plan to extend the trust-cert script functionality to make it responsible for certificates installation and removal.

[waldekmastykarz]

For removal, let's create a separate script to keep them simple and single-responsibility