deskutils/plan: Add Family Day (Canada)

The various Canadian provinces and territories have added a new
provincial holiday called in most provinces Family Day. Though,
it is called Louis Riel Day in Manitoba, Islandar Day in
Prince Edward Island, Nova Scotia Heritage Day in that province,
and Yukon Heritage Day in that territory. It is generally called
Family Day because all other Canadian provinces call it that.

Family Day falls on the same day as President's Day does in the US.

See also: https://en.wikipedia.org/wiki/Family_Day_(Canada)

		https://www2.gov.bc.ca/gov/content/governments/ \
			celebrating-british-columbia/bc-family-day
		https://www.statutoryholidays.com/family-day.php