Users with 24-hour time set in preferences cannot add course sections

[david-mcpherson]

The convertTo24 function assumes that the time will look like "9:30 a.m.", with an "a.m/p.m" suffix.

Here's the console error for users with 24 hour time:

The solution is to make the "a.m/p.m" part of the regex optional:

[david-mcpherson]

PR opened: https://github.com/mlool/workday-calendar-extension/pull/6