Highlight Operator Framework Community Google Calendar

Updates the project's README.md to include a link to the Operator
Framework Community Meetings Google Calendar. This addresses an issue
where new member's of our associated Google Groups are not automatically
invited to existing calendar events.

Signed-off-by: Alexander Greene <greene.al1991@gmail.com>

README.md

@@ -13,6 +13,8 @@ Discuss on:
 
 ## Meetings
 
+You can see all operator-framework meetings by adding this [Google Calendar](https://calendar.google.com/calendar/u/0?cid=YzA0OGUxY2YzM2ZjOGZiYTFjNjVlZjMxZGJiNGVhNDdkZTYxZTlhYzNlODcwZmY5OGM2Mjk5NDVjZTVlZGMyYkBncm91cC5jYWxlbmRhci5nb29nbGUuY29t)
+
 ### Operator Framework Special Interest Group
 
 * Next Scheduled Meeting: November 12 2019  16:00 UTC/9:00 am Pacfic/Noon Eastern [dial-in details](https://github.com/operator-framework/community/projects/2#card-27939134)