Add Myanmar holidays

[arkid15r]

Links:

• https://en.wikipedia.org/wiki/Public_holidays_in_Myanmar
• https://www.timeanddate.com/holidays/myanmar/
• https://evisa.moip.gov.mm/home/publicholiday
• https://myanmar.gov.mm/upcoming-holidays

[PPsyrius]

Note on this: Myanmar need its own traditional Burmese Calendar to be mapped out first for their Buddhist Holidays - akin to the Indochinese ones used by Thailand, Laos, and Cambodia.