Support `@returns`

[dipterix]

Currently find_missing_tags checks @return, but it seems the new roxygen2 encourage people to use @returns

[statnmap]

Thanks. We'll see what we can do.
If you want to implement the fix with a PR, we can guide you through the process

More info:
roxygen2 7.0.0: * New @returns is an alias for @return (#952) - https://github.com/r-lib/roxygen2/blob/a34bdf7c7b952068b1f7742b7b34d1eac78e54da/NEWS.md?plain=1#L314

- name: return
  description: >
    Describe the function's output. Superseded in favour of `@returns`.
  template: ' ${1:description}'
  vignette: rd

https://github.com/r-lib/roxygen2/blob/a34bdf7c7b952068b1f7742b7b34d1eac78e54da/inst/roxygen2-tags.yml#L335