add Royal Wedding bank holiday

Signed-off-by: Sebastian Freundt <hroptatyr@fresse.org>
update uids in all holiday .ics files

Signed-off-by: Sebastian Freundt <hroptatyr@fresse.org>
add holidays for the United States of America and subdivisions

Signed-off-by: Sebastian Freundt <hroptatyr@fresse.org>