Some timezones not available in selector

[marvinruder]

I would like to use ProjectSend in UTC timezone. However, likely due to the condition in

projectsend/includes/forms/options/timezones.php

Lines 34 to 44 in d40be9e

	if ($continent == 'Africa'
	|| $continent == 'America'
	|| $continent == 'Antarctica'
	|| $continent == 'Arctic'
	|| $continent == 'Asia'
	|| $continent == 'Atlantic'
	|| $continent == 'Australia'
	|| $continent == 'Europe'
	|| $continent == 'Indian'
	|| $continent == 'Pacific'
	) {

the timezone Etc/UTC is not rendered as an option in the timezone selector at /options.php?section=general.

When I manually set timezone to Etc/UTC in the tbl_options database table, it appears to be respected, but the selector shows the first option Africa/Abidjan as selected and also stores that value everytime I want to change different settings on the same page.

Would it be possible to add all available time zones to the selector, perhaps grouped in an Other section?