Add block separators to EV3 extension

[kyleplo]

Expected Behavior

There are block separators.

Actual Behavior

There are not.

Steps to Reproduce

Add the EV3 extension and look between the blocks.

Operating System and Browser

All.

Note

I can probably do this if you mark as help wanted.

[thisandagain]

@cwillisf @ericrosenbaum If I remember correctly we do not yet have a way of doing block separators in extensions. Can you confirm?

[kyleplo]

@thisandagain There is a way: https://github.com/LLK/scratch-vm/blob/develop/src/extensions/scratch3_microbit/index.js#L691

[thisandagain]

@ericrosenbaum Can you advise on where/if you would like block separators?