Add documentation for GCal multiCalendar support

_site/content/posts/modules/gcal.md

@@ -44,6 +44,7 @@ gcal:
   email: "chriscummer@me.com"
   enabled: true
   eventCount: 12
+  multiCalendar: true
   position:
     top: 0
     left: 0
@@ -105,6 +106,11 @@ Values: `true`, `false`.
 The number of calendar events to display. <br />
 Values: A positive integer, `0..n`.
 
+`multiCalendar` <br />
+Whether or not to display your primary calendar or all calendars you
+have access to. <br />
+Values: `true`, or `false`
+
 `position` <br />
 Where in the grid this module's widget will be displayed. <br />