Link sooner to the list of Tech Days for the current year

Now that we're linking to this page a bit more from various places,
having an easy way from here to the events for the current year
seems like it's useful.

Author: PeterJCLaw

robots_101/tech_days.md

@@ -5,6 +5,8 @@ title: Robots 101 - Tech Days
 
 # Robots 101 - Tech Days
 
+_See the Tech Days for this year in the [events calendar][events-calendar] on our website._
+
 Tech Days are opportunities for your team to spend a whole day working on your
 robot, with lots of help available. They’re also an opportunity to see how other
 teams are doing or get more direct help with your robot.