Suggestion: allow files to be skipped

[dmurdoch]

The suggestion is to allow a meta option like skip = c("filename.R") which would make Roxygen completely ignore that source file. (It might make sense to use a regular expression, but this is likely a rare enough need that exact filename matches are probably good enough.)

The motivation for this was described here: https://stat.ethz.ch/pipermail/r-package-devel/2024q4/011250.html . In summary, the issue is that .R files may contain code that should not be executed by Roxygen. When the load strategy is "source" or "pkgload", that code will be executed.

My current workaround is to use load strategy "installed", and it works, but it's less convenient than the others, because I may have to install, document, then install again after a change to the code in the package or I will see a stale help page.