Candidate fix #117

[maksymiuks]

Here is the candidate fix for the issue mentioned here https://github.com/r-lib/vdiffr/issues/117#issuecomment-1243856829

It looks to be as simple as removing the statement that blocks the execution for R 4.1.x and above. Additionally, I added a decor package to suggests dependencies. My tests on the fresh R installation (MacOS) showed that decor is required by cpp11 which is required by roxygen2 for the execution of unit tests embedded in this package. Therefore I think it's appropriate to add it as a dependency so it can be tested in a fresh installation. This is just a suggestion, I'm happy to remove that one.

Requesting review @lionel-

[maksymiuks]

I'm not sure why windows build is failing but it does not seem to be related to my change