feat(cli): add exp task create command (#19492)

Partially implements https://github.com/coder/internal/issues/893

This isn't the full implementation of `coder exp tasks create` as
defined in the issue, but it is the minimum required to create a task.

cli/exp_task.go

@@ -14,6 +14,7 @@ func (r *RootCmd) tasksCommand() *serpent.Command {
 		},
 		Children: []*serpent.Command{
 			r.taskList(),
+			r.taskCreate(),
 		},
 	}
 	return cmd