[feat] Add community calendar (#3037)

* [feat] Add community calendar

* Address comments by evankanderson@ more details

* fix typo

Author: Carlos Santana

community/calendar/_index.md

@@ -0,0 +1,13 @@
+---
+title: "Knative Community Calendar"
+linkTitle: "Community Calendar"
+weight: 29
+showlandingtoc: "false"
+type: "docs"
+---
+
+The [Knative Community Calendar](https://calendar.google.com/calendar/u/0/[email protected]) contain events that provides the opportunity to learn more about Knative and meet other Knative users and contributors.
+
+Events don't have to be organized by the Knative project to be added to the calendar. If you want to add an event to the calendar please send an email to [[email protected]](mailto:[email protected]) or post to the #community channel in the Knative [Slack](https://slack.knative.dev) workspace.
+
+<iframe src="https://calendar.google.com/calendar/embed?height=600&amp;wkst=1&amp;bgcolor=%23ffffff&amp;src=Y190Y3V0MHRiazAxNmcyMmNzcTFjZWQ5bHFkOEBncm91cC5jYWxlbmRhci5nb29nbGUuY29t&amp;color=%23D81B60" style="border:solid 1px #777" width="100%" height="600" frameborder="0" scrolling="no"></iframe>