command: hard wrap help message flags

This greatly improves readability when lots of flags are registered.

Signed-off-by: Ophestra <cat@gensokyo.uk>

command/node.go

@@ -3,7 +3,6 @@ package command
 import (
 	"flag"
 	"io"
-	"strings"
 )
 
 // A node represents a command.
@@ -17,7 +16,7 @@ type node struct {
 	// Names of commands preceding node.
 	prefix []string
 	// Short user-facing representations of flags received by node.
-	suffix strings.Builder
+	suffix []string
 
 	f   HandlerFunc
 	set *flag.FlagSet