Feature Request: import_list recursively importing files that contain lists

[billdenney]

Please specify whether your issue is about:

• [x] a suggested code or documentation change, improvement to the code, or feature request

I often receive xls(x) files where I need to load all sheets from all files. Currently, I run lapply(X=setNames(all_filenames, basename(all_filenames)), FUN=import_list). It seems like it could be a useful feature to be able to run the equivalent of the above with something like import_list(all_filenames, recursive=TRUE) where recursive=TRUE means that the above would be called as lapply(X=setNames(all_filenames, basename(all_filenames)), FUN=import_list, recursive=FALSE).

If of interest, I would be happy to create a PR.