pxt-microbit Accessibility PR (#529)

* Accessibility changes

docs/projects/telegraph/code.md

@@ -4,7 +4,7 @@ Let's build the code that, when the user presses the button ``A`` on a @boardnam
 
 Make sure that the sending and receiving wires run symmetrically across: pin ``P1`` on one @boardname@ is connected to pin ``P2`` on the other, and vice versa, as shown on the pictures in the "Make" section. This way we can use the same code on both @boardname@s .
 
-### Step 1
+## Step 1
 
 We start with a block that digitally writes **high** (value ``1``) to the sending @boardname@'s pin ``P1``. This block can be found in _Pins_ drawer of the Advanced section.
 
@@ -12,7 +12,7 @@ We start with a block that digitally writes **high** (value ``1``) to the sendin
 pins.digitalWritePin(DigitalPin.P1, 1)
 ```
 
-### Step 2
+## Step 2
 
 To show what we are sending, we add a block to turn on an LED in the centre of the LED display (2,2) using _plot x, y_ :
 
@@ -21,7 +21,7 @@ pins.digitalWritePin(DigitalPin.P1, 1)
 led.plot(2, 2)
 ```
 
-### Step 3
+## Step 3
 
 Now that we know how to send the signal, we only want to be doing it while the button ``A`` is pressed. 
 Pick an _if_ block from the _Logic_ drawer (you'll need the version with _else_ part that will remain empty for now). Add a check whether the button ``A`` is pressed from the _Input_ drawer and move the blocks from the previous step into _then_ part :
@@ -34,7 +34,7 @@ if (input.buttonIsPressed(Button.A)) {
 ```
 
 
-### Step 4
+## Step 4
 
 For the _else_ branch (while the button A is not pressed) we want to do the opposite of what we did in the _then_ branch: take the value of pin ``P1`` to **low** (0) and unplot the corresponding LED on the sending @boardname@ :
 
@@ -48,7 +48,7 @@ if (input.buttonIsPressed(Button.A)) {
 }
 ```
 
-### Step 5
+## Step 5
 
 Let's wrap it all in a forever loop so this code runs in the background, forever checking the button ``A`` and sending the appropriate signal to the receiver.
 Modify your code so that your code looks like this. Download the code into one of the @boardname@s, press and release button ``A`` a few times.
@@ -67,7 +67,7 @@ basic.forever(() => {
 
 The sending part is done, so we are going to add the receiving part.
 
-### Step 6
+## Step 6
 
 The receiver needs to digitally read from the pin to which the sending @boardname@ will be writing (``P2``) over the wire. Let's start by going to the _Pin_ drawer, adding digital read pin ``P0`` and changing the pin value to ``P2``.
 Now we want to examine the value read from ``P2`` and check whether it is **high** (value ``1``) or not. Go to the _Logic_ drawer, first pick an _if_ block, then come back for a comparison operator (=). Plug in our digital read block as one operand and the value ``1`` as the other.
@@ -93,7 +93,7 @@ basic.forever(() => {
 
 Your telegraph is ready!
 
-### Step 7
+## Step 7
 
 * Connect the first @boardname@ to your computer using your USB cable and download the telegraph script to it.
 * Connect the second @boardname@ to your computer using your USB cable and download the telegraph script to it.