Redesign calendar page

[ettolrach]

The event calendar is still used (as of InfBall 2021), so we should probably give more attention. There are four previous issues in this repo which we should consider:

• List previous events on the page, not just upcoming ones. calendar: don't link directly to the calendar (for list of all events) #51
• Pull Facebook events to the calendar automatically and if a link can be provided, include it. calendar: link to "event page", nothing otherwise #52
• Have a 'Add to Google Calendar' link on our page, not just the Google Calendar. calendar: "add to gcal" link #53
• 'Overhaul events page', so a general redesign (maybe the graphic designer can take a look at this?). overhaul events page #65

[yutotakano]

Unrelated, but infball 20212 :)

I did a small change in a pull request last November that added a bit more detail, but the page does still look quite plain. Something pretty like the Edinburgh Hoppers event page would be amazing!

[yutotakano]

Not sure what the state #65 aims to get it to, but I've made the full calendar page have past events and be more interactive and nicer. With the previous update above, I had the page show only near-future events, but since this is done by the index page carousel instead, the page shows a full monthly calendar with past events too.

[ettolrach]

It's been redesigned here, do we want to close this? I'm not sure whether it automatically pulls in Facebook events but we don't use that anymore, though we probably want to if the social media officer wants to make use of Facebook.