Add Toronto Stock Exchange (TSX) definitions

[selesse]

The Toronto Stock Exchange (TSX) definitions are very close, but not quite to Canada's Ontario holidays. The only difference is that the TSX also observes Civic Holiday.

I have validated that these definitions match the dates provided on the TSX's website:

irb(main):035:0> Holidays.load_custom(File.expand_path('~/git/definitions/tsx.yaml')); nil
=> nil
irb(main):036:0> Holidays.between(Date.civil(2022, 1, 1), Date.civil(2022, 12, 31), :tsx, :observed).each { |h| puts h[:date].to_s + " => " + h[:name] }
2022-01-03 => New Year's Day
2022-02-21 => Family Day
2022-04-15 => Good Friday
2022-05-23 => Victoria Day
2022-07-01 => Canada Day
2022-08-01 => Civic Holiday
2022-09-05 => Labour Day
2022-10-10 => Thanksgiving
2022-12-26 => Christmas Day
2022-12-27 => Boxing Day
irb(main):037:0> Holidays.between(Date.civil(2021, 1, 1), Date.civil(2021, 12, 31), :tsx, :observed).each { |h| puts h[:date].to_s + " => " + h[:name] }
2021-01-01 => New Year's Day
2021-02-15 => Family Day
2021-04-02 => Good Friday
2021-05-24 => Victoria Day
2021-07-01 => Canada Day
2021-08-02 => Civic Holiday
2021-09-06 => Labour Day
2021-10-11 => Thanksgiving
2021-12-27 => Christmas Day
2021-12-28 => Boxing Day

Process

I copy/pasted the relevant holidays from ca.yaml, renamed the region to tsx. I also copied the relevant tests. make validate ran successfully. I also made sure the code coverage was 100%, opened #213 to make sure the contribution guidelines were clearer on this point.