feat: mapping short flags

[mfridman]

Map short flags to their long versions (e.g., -f maps to --file). Not sure if we want to do this, but opening this up as it may come up.

Maybe something like this:

root := &cli.Command{
	Flags: cli.FlagsFunc(func(f *flag.FlagSet) {
		f.String("file", "", "path to the tasks file")
	}),
	FlagsMetadata: []cli.FlagMetadata{
		{Name: "file", Required: true, Short: "f"},
	},
}

This would mean all forms would be supported:

-f file.txt
--f file.txt
-file file.txt
--file file.txt

Then, we need to decide on how to render the usage information:

Usage:
  app [command] [flags]

Flags:
  -f, --file string   Path to config file (default "config.yaml")