Document passing arguments to externals better

[kubouch]

I've seen a lot of issues about external arguments, like this one: nushell/nushell#5947.

We should have a page that documents all the ways you can call external with arguments (i.e., explaining that you can pass a list to an external as a list of arguments and that one long string with spaces will be considered as one argument).

[WindSoilder]

Wow... That's what I meet and confused before

[kubouch]

Also, you can run externals with ^$program-name, that should be documented as well since it might not be obvious but it's very useful.

[Kissaki]

There is no specific documentation for calling external [with or without ^] yet, right?

I assume Externs as well as an earlier introduction would be the places to put documentation about calling external executables?