Add the ability to link route links within the description on the calendar

[onewheelskyward]

As a user, I want to see route links hyperlinked on the web calendar. Currently it just displays it as text.

There are a couple of ways to accomplish this:

1. maintain an allow-list of domains which we will allow links (to avoid spam)
2. create a rich text input with markdown allowing folks to also add formatting to their text

Acceptance means ridewithgps.com links will be hyperlinked on the calendar page.