Date.now().next().weekend() does not behave the same as Date.now().next().weekday()

[CDSimpson]

I've noticed that the implementations of weekend() and weekday() are not the same. The weekend() function appears to only work when chaining with is(), while weekday() will work with incrementing as well (via the addWeekdays() prototype method). I could work around this limitation by explicitly checking for saturday() or sunday(), but it would be nice to be able to use the weekend() function in the exact same ways that you can use the weekday() function.