Multiple files or urls as input

This relates to multiple objects in the same input, but is a bit different.

Would be useful to allow more than one input on the command line:

gron <file|url> <file|url> ... etc

It's hard to say exactly what gron should output in this case, possibly each object field could inherit the file or url name.

e.g.

gron file1.json file2.json

file1.keyValue = "fish" file2.keyValue = "chips"

or perhaps more simply, number the files, which would avoid file name clashes (and could also support multiple objects in streams.)

[0].keyValue = "fish" [1].keyValue = "chips"

at the moment, I for this, which isn't quite as good: echo *.json | xargs -n1 gron >> out.txt