Add calendar of Nordic ESM events

[annefou]

Problem:
We can easily add new events in nordicesmhub.github.io by creating a new markdown file in _events directory but it does not automatically add it to the google calendar.

Task: Have a calendar that is automatically updated (new entry added) every time someone adds a new event in _events directory.

Comment: we do not have to keep a Google calendar. According we have a calendar we can browse from the website.

[annefou]

Done