makecode: screenshot ignores display shield

[bragrseg]

When creating a program in makecode that makes use of the display shield, the screenshot functionality ignores it.
makecode includes functionality to take a screenshot of the micro:bit when it is running, however if you are running a program which uses the display shield it does not take a screenshot of it, instead it still only does the micro:bit

reproduce:
create a program in makecode that makes use of an extension that uses the display shield.
press the screenshot button underneath the micro:bit and display shield