Post-ship resolutions to the events page

[mattxwang]

Tracking issue developed off of the comments in #272:

• on the calendar itself
  • some of the other views are what I would call "low in design quality", since there is no corresponding mockup. the agenda view is particularly bad.
  • similarly, mobile view is subpar
  • there are contrast issues with the white text on the gradient
  • in general, I don't think this calendar is very accessible, though I haven't had much time to test.
• on the event structure
  • currently there is no particular support for virtual/in-person events, or highlighting things like zoom links, feedback forms, or resources. we didn't have this in the design, but might be good to do!
• on the script
  • no support for image parsing or alt text retrieval; this is rather complicated given our technical constraints (see events subtask: converting marketing spreadsheet to new event.js #281)
  • link support is hard-coded; there is no support for Zoom, IG, Itch, Discord, Google Forms, GitHub, etc.
  • no support for all-day events
  • the generated description does not apply link effects or any markdown-esque styling
  • currently, there is no mechanism to merge the output of the script with the existing input; this is going to be a headache down the line
  • id offset is hard-coded
  • little field validation is done
  • the recurring week range requires a slightly different column format than what we have now - 2021-10-04 - 2021-12-01 instead of relying on the quarter system
  • lots of things are hard-coded, so we'll need to keep an eye out for minor human errors