Add output folder for bicep snapshot command

**Is your feature request related to a problem? Please describe.**
I am experimenting with the bicep snapshot command and the first thing I notice is that there is no option to set de creation folder of the snapshot.

**Describe the solution you'd like**
for me this command is a type of test and so i want this generated json file in a test folder and not in my parameters folder.

so it would be great if we could add the param --outfile like we have with the bicep build(-params) commands.