Add fundraising meetings to calendar

wiki/src/contribute/calendar.mdwn

@@ -13,10 +13,20 @@ All times are referenced to Berlin and Paris time.
 
 * 2019-05-23 and 2019-05-24: Buster (remote) sprint
 
+* 2019-05-28, 14:00 TB meeting
+
+* 2019-05-29, 16:00 Fundraising meeting
+
 * 2019-06-03, 16:00: [[Foundations Team|contribute/working_together/roles/foundations_team]] meeting
 
+* 2019-06-04, 11:00-15:00 Fundraising work meeting
+
+* 2019-06-11, 16:00 Fundraising meeting
+
 * 2019-06-17 and 2019-06-18: Buster (remote) sprint
 
+* 2019-06-25, 16:00 Fundraising meeting
+
 * 2019-06-25 to 2019-06-27: Translation platform sprint
 
 * 2019-07-03, 16:00: [[Foundations Team|contribute/working_together/roles/foundations_team]] meeting