adds `\donttest{}` tag in examples with {MAE}

[averissimo]

Pull Request

(from CRAN) ... Lengthy examples (> 5 sec), can be wrapped in \donttest{}. ...

Partially fixes #554

Remaining examples will be addressed by #550

Changes description

• Changes @examplesIf requireNamespace("MAE") in favor of inline conditional clause
• Surrounds {MAE} dependent examples with \donttest{} to avoid slow examples

[chlebowa]

Can @examplesIf be put under \donttest?

[averissimo]

Nop, I tested it before and again just now

[averissimo]

And I couldn't find an elegant way of doing this.

For instance rlang::is_installed(...) also takes "equal" time.

Maybe we can improve on this later on. If not, when breaking up the pkg in 2 will sort of solve this.