Update and add screenshots for hex download (#1492)

* Update and add screenshots for hex download

* punctuate the pause

docs/device/usb/windows-edge.md

@@ -46,8 +46,13 @@ A message will appear at the bottom of the browser asking what you want to do
 with the file. 
 
 4. Click **Save As**
+
+![Save download file dialog](/static/mb/device/usb/save-as-edge.gif)
+
 5. Save the ``.hex`` file into the **MICROBIT** drive
 
+![Save hex file to MICROBIT drive](/static/mb/device/usb/save-as-windows.png)
+
 ## Step 3: Transfer the file to your micro:bit
 
 * The LED on the back of your micro:bit flashes during the transfer (which 

docs/device/usb/windows-firefox.md

@@ -36,14 +36,21 @@ it appears as a new drive under Devices.
 
 ## Step 2: Download your program
 
-1. Open your project on @homeurl@
-2. Click **Download**
+1. Open your project on @homeurl@.
+2. Click **Download**.
 3. When prompted, choose to **save** the compiled file onto your computer. The
    prompt will be different depending on which browser you are using, or
-   whether you are using a Windows computer or a Mac
+   whether you are using a Windows computer or a Mac.
 
-A window will appear asking whether you want to save or open the `.hex` file.
-Select **Save As** and save it to the MICROBIT drive.
+![Save download file dialog](/static/mb/device/usb/save-file-firefox.gif)
+
+A window may appear asking whether you want to save or open the `.hex` file. If it doesn't, go click on the downloads icon at the top of the browser.
+
+![Save file prompt](/static/mb/device/usb/open-file-firefox.png)
+
+Click the folder icon and copy the file from the list of downloads to the **MICROBIT** drive.
+
+![Move hex file to MICROBIT drive](/static/mb/device/usb/move-hex-file-firefox.png)
 
 ## Step 3: Transfer the file to your micro:bit
 

docs/device/usb/windows-ie.md

@@ -44,7 +44,11 @@ it appears as a new drive under Devices.
 A message will appear at the bottom of the browser asking what you want to do
 with the file. Click **on the arrow next to Save** and click **Save As**
 
-In the save dialog, save the ``.hex`` file to the MICROBIT drive.
+![Save download file dialog](/static/mb/device/usb/save-as-ie.gif)
+
+In the save dialog, save as the ``.hex`` file to the MICROBIT drive.
+
+![Save hex file to MICROBIT drive](/static/mb/device/usb/save-as-windows.png)
 
 ## Step 3: Transfer the file to your micro:bit