Switch to calendar ICS file hosted on GitHub pages

Some people like having a calendar invite for our meetings.  We've
been using Google Calendar to achieve this.  However, this calendar
can be troublesome to update and has often lagged our real schedule.

Other teams were having this same issue, so @davidtwco graciously
created a pair of projects to solve this problem:

- https://github.com/rust-lang/calendar
- https://github.com/rust-lang/calendar-generation

The tooling here allows for our calendar to be specified in TOML and
tracked in git.  From this, it generates an `ical` ICS file that is
hosted on GitHub pages.

All of the lang team and subteam meetings that were previously on the
other calendar have been added to this new calendar.  Let's switch
over to it.

(People will, unfortunately, have to make a one-time update to their
calendars with this new URL.)

To make our meetings more accessible to people who don't view the
calendar, let's go ahead and describe the time of our recurring slots
directly on the calendar page.  We'll describe these in terms of
U.S. time zones because we track U.S. daylight saving time.

Let's also update this page to note that design meeting minutes can be
found via the issue for each design meeting, and let's link to our
documents on HackMD that include the more recent minutes until they
are archived to git.

Finally, we had linked on this page to the style team's calendar.
However, the links to that calendar now return HTTP error 404.  Let's
remove those apparently dead links.

src/calendar.md

@@ -1,27 +1,34 @@
 # Calendar
 
-We have a lang-team calendar that shows the time for our various meetings.
-Meetings are generally open to anyone who wants to listen in. We also try to
-post [minutes](https://github.com/rust-lang/lang-team/tree/master/minutes) (and recordings, if any) on a "best-effort" basis from our
-meetings.
+The lang team has two recurring weekly meeting slots:
 
-- [View calendar][caldav] -- use this to view the calendar online and add it to your Google Calendar
-- [ICS file, for use outside from google calendar][ics] -- you can use this to subscribe from other programs
+- [Triage meetings](./meetings/triage.html): Weekly on Wednesdays at 11:00 U.S. Eastern Time.
+- [Design/planning meetings](./meetings/design.html): Weekly on Wednesdays at 13:00 U.S. Eastern Time.
 
-You can find a list of upcoming design meetings here:
+When adjusting for other time zones, note that our meeting times follow changes in the particulars of U.S. daylight saving time.
 
-- [Design meeting schedule][ghp]
+For the design/planning meeting slot, we typically do a planning meeting on the first Wednesday of the month, then we do design meetings on each remaining Wednesday.
 
-## Subteam Calendars
+Our meetings are open to all those who are interested to listen.
+
+To subscribe to the calendar of our recurring meetings, add this URL to your favorite calendaring application:
+
+- <https://rust-lang.github.io/calendar/lang.ics>
+
+Our schedule of upcoming design meetings is tracked in a GitHub project and can be viewed here:
+
+- [Design meeting schedule](https://github.com/orgs/rust-lang/projects/31/views/10)
 
-Some subteams of the lang team reuse the primary lang team calendar for their own calendar events, while others may choose to create a separate calendar. The calendars of all subteams that do not use the main calendar should be listed below:
+Each design meeting issue includes details about what we'll be discussing. After the meeting, the issue will include a link to the minutes.
 
-### Style Team
+Minutes for all of our recent meetings can be found here:
 
-- [View calendar](https://calendar.google.com/calendar/embed?src=d0564ed914a41cf4915bd5ebe6e2e4ec0ee1293fdc1d09d6f5bdb27d4f91c083%40group.calendar.google.com)
-- [ICS file](https://calendar.google.com/calendar/ical/d0564ed914a41cf4915bd5ebe6e2e4ec0ee1293fdc1d09d6f5bdb27d4f91c083%40group.calendar.google.com/public/basic.ics)
+- [Lang team documents on HackMD](https://hackmd.io/@rust-lang-team)
+
+Periodically, we archive our meeting minutes to git:
+
+- [Lang team archived minutes](https://github.com/rust-lang/lang-team/tree/master/minutes)
+
+## Subteam Calendars
 
-[caldav]: https://calendar.google.com/calendar/embed?src=recud4b9o8cmc0m5rmr033p5nk%40group.calendar.google.com
-[ics]: https://calendar.google.com/calendar/ical/recud4b9o8cmc0m5rmr033p5nk%40group.calendar.google.com/public/basic.ics
-[main meeting]: https://calendar.google.com/event?action=TEMPLATE&tmeid=NmU4ajUyaWpmaHZic2YzYXVxa25rcnIyZHRfMjAxOTA0MTFUMTkwMDAwWiByZWN1ZDRiOW84Y21jMG01cm1yMDMzcDVua0Bn&tmsrc=recud4b9o8cmc0m5rmr033p5nk%40group.calendar.google.com&scp=ALL
-[ghp]: https://github.com/orgs/rust-lang/projects/31/views/10
+Some subteams of the lang team reuse the primary lang team calendar for their own calendar events, while others may choose to create a separate calendar. We'll list below the calendars of all subteams that do not use the main calendar.