pxt-microbit Accessibility PR (#529)

* Accessibility changes

docs/lessons/magic-8/activity.md

@@ -114,9 +114,9 @@ input.onGesture(Gesture.Shake, () =>  {
 })
 ```
 
-### ~avatar avatar
+## ~avatar avatar
 
 Excellent, you're ready to continue with the [challenges](/lessons/magic-8/challenges)!
 
-### ~
+## ~
 

docs/lessons/magic-8/challenges.md

@@ -26,7 +26,7 @@ input.onGesture(Gesture.Shake, () =>  {
 ```
 
 
-### Challenge 1
+## Challenge 1
 
 Now let's increase the number of responses the magic 8 ball can give. How about 5 responses instead? Let's change the limit of `pick random` to  4.
 
@@ -49,7 +49,7 @@ input.onGesture(Gesture.Shake, () =>  {
 })
 ```
 
-### Challenge 2
+## Challenge 2
 
 Now have the magic 8 ball respond "Try again" if **randomNumber** is 3.
 
@@ -73,7 +73,7 @@ input.onGesture(Gesture.Shake, () => {
 })
 ```
 
-### Challenge 3
+## Challenge 3
 
 Now what about if **randomNumber** is 4? Let's have the magic 8 ball respond "Definitely!".
 

docs/lessons/magic-8/tutorial.md

@@ -2,7 +2,7 @@
 
 Show a string to instruct the user how to play Magic 8! The magic 8 ball can only answer questions with "YES", "NO", or "MAYBE"...
 
-### Rebuild the game!
+## Rebuild the game!
 
 The blocks have been shuffled! Put them back together so that...
 * show "ASK A QUESTION" on the screen