Improve documentation for engine arguments

[juliasilge]

Let's improve documentation for how to use engine arguments.

• We can expand the set_engine() documentation with another example as well as better text explanation of engine arguments (@details).
• We can create a little template about engine arguments to add to the main model pages so when folks are looking for specific arguments they see a nudge to understand engine arguments.

[topepo]

This should wait until #631 is merged

[github-actions]

This issue has been automatically locked. If you believe you have found a related problem, please file a new issue (with a reprex: https://reprex.tidyverse.org) and link to this issue.