Documentation: Example error

[mpettis]

From the main page at: https://nbenn.github.io/mockthat/

We have this example, which I suspect is broken because you need to reinstall mockr before running:

mockr::with_mock(
  foo = function(x) "bar",
  met(x)
)
#> Error in loadNamespace(x): there is no package called 'mockr'