Create cronjob for checking comp announcements/registration openings in Slovakia

[jakubdrobny]

• [ ] restructure posting announcements like posting new competitions
• [ ] create custom functions to post automated announcements checking on wca for newly announced competitions in Slovakia and competitions in Slovakia, whose registration period starts in the next day
• [ ] create file running these cronjobs next to WeeklyCompetitionJob.go, called RegistrationOpeningJob.go and CompetitionAnnouncementJob.go
• [ ] create 2 cron jobs running these two files once a day