request: error customization

[kyranet]

Is your feature request related to a problem? Please describe.

Sometimes, admins may want to customize the error message Skyra sends, for example, in a slap command, the admin may want Skyra to send Who do you want to slap? when the argument fails to be resolved, instead of the generic You must provide a valid user.

Describe the solution you'd like

We can use #{str} inside tags, e.g:

{author} gave {user #{Who do you want to slap?}} a big slap! {random {url1} {url2} {url3} {url4}} (complementing #1).

Error messages are not affected by transformations - because they're not part of the output message, but an error.

It can also be weird if somebody did Echo: {string... #{Please specify the content} | bold | uppercase}, the admin expects this to return Echo: **SUCH WOW** when somebody runs it with s!mycommand such wow, but it's hardly expectable in the error itself - which would show **PLEASE SPECIFY THE CONTENT** if it did.

Describe alternatives you've considered

N/a.

Additional context

N/a.