Support list of arguments for task options

[mspoerer]

First of all I want to thank you guys for that awesome work you are doing. I am currently using xclap in combination with nix-clap in a bunch of projects. And everything worked fine... till now. Currently I have to provide a list of args for a specific task option. It seams that xclap does not support that out of the box.

Expected Behaviour clap <task> --foo value1 value2 --bar Task option foo gets list of values.

Current Behaviour value1 gets interpreted as new task. Error Message: No task namespace value1 exists.