Add --force option to network rm subcommand

The code is similar to that used by the volume rm subcommand, however,
one difference I noticed was VolumeRemove takes the force flag/option
was a parameter. This isn't the case for NetworkRemove.

To get NetworkRemove to take a similar parameter, this would require
modifying the Docker daemon. For now this isn't a route I wish to take
when the code can be arrange to mimic the same behavior.

Co-authored-by: Sebastiaan van Stijn <github@gone.nl>
Signed-off-by: Conner Crosby <conner@cavcrosby.tech>

docs/reference/commandline/network_rm.md

@@ -15,7 +15,7 @@ Aliases:
   rm, remove
 
 Options:
-      --help   Print usage
+  -f, --force   Do not error if the network does not exist
 ```
 
 ## Description