Vmisc::pkg_switch_default should show what versions are available in the library 

I just installed a really old version of `plotly` and then made it default with that function. Now I don't know how to bring back my old default to the latest version. I *can* do

```r
pkgs <- list.files(.libPaths()[1])
pkgs[grep("plotly", pkgs)]
```

which tells me:
```
[1] "plotly"        "plotly-4.10.4"
```

but I should make that easier