Add Canadian national and provincial holidays

Uses moveable holidays, where holidays depend on certain weekday or are bound to a certain day of the month. Provincial holidays may be optional depending on employer or region.

The `getMovableEventsForYear()` function now includes the variable holidays. It would be cleaner to specify the rules in the `holidays` object instead of hard-coding them; I'm not sure if you have plans for this or want to wait for more input and settle on a more generalized solution/library.