Add the use-upkeep_issue checklist to the manual page #1862

[ndjrt]

Fixes #1862

[jennybc]

Thanks @ndjrt! My first inclination is that we'd want to populate this programmatically, i.e. to actually hit the code that generates the checklist. This guarantees that the docs match the code. Now this is actually kind of hard/fiddly, which is why this hasn't been solved yet!

The technology you'd use to do this is here:

https://roxygen2.r-lib.org/articles/rd-formatting.html#code-chunks

It's still not simple, because you'd have to point at a fake package and/or call an unexported helper, both of which require some thought. So if you're interested in continuing the effort, that's what needs to be explored. It's possible that we decide this is more trouble than it's worth, but it would be interesting to take a crack at this and see how feasible it is. The tests related to upkeep are a great place to start for inspiration.