Set working directory OS-dependent with `setwdOS`

Due to work-related, system exclusive software, I got used to switching from Linux to Windows, and vice versa, quite often. Since rebooting the system under Linux every time I wanted to do a little coding in between seemed inconvenient, I usually included a simple `switch` command in the beginning of my code to identify the current OS (via `Sys.info()[["sysname"]]` and set the working directory accordingly. These few lines of code are now available as a function, which might come in handy for folks switching between different OS as often as I do.

The usage is almost self-explanatory.

    ## os partition without file path extension
    setwdOS()

    ## with file path extension
    setwdOS(path_ext = "kilimanjaro/nubiscope")