Use `with(` calls instead of `library(` in examples

[Melkiades]

This comes from #804

[shajoezhu]

@Melkiades , do you mean global change library to with?

[Melkiades]

I think it is in general used as on.exit for packages used locally but I do not know if it is actually faster or better. https://withr.r-lib.org/articles/changing-and-restoring-state.html

We should discuss this possible enhancement. Surely it should be used for local changes (e.g. options)