HID extensions doesn't work as expected. #312

Describe the bug
Code with HID based extensions i.e. keyboard, mouse, gamepad doesn't work unless I add a pause in on start block.

To Reproduce
Steps to reproduce the behavior:

1. Goto maker.makecode.com and create a new project.
2. select any board with usb host supported like feather M0 express.
3. add any of the HID extensions i.e. keyboard, mouse, gamepad.
4. add a block from the extension to the on start or forever block.
5. pair and upload the code to the board.

Expected behavior
OS should recognize the respective device and should function as expected.

Actual behaviour
OS doesn't recognize any device.

workaround
just add a pause of atlease 100ms on the on start block

potential fix
the board should wait for HID to initialize before starting the code.

Desktop (please complete the following information):

• OS: Ubuntu 18.04 LTS
• Browser Chrome
• Version 81.0.4044.122 (Official Build) (64-bit)

Additional context
test code:
not working
working