Highlight the item loaded by list blocks

[apple502j]

Expected Behavior

The item on the stage monitor loaded by list blocks should be highlighted.

Actual Behavior

Not implemented.

Steps to Reproduce

1. Open https://scratch.mit.edu/projects/230003247/
2. Open https://llk.github.io/scratch-gui/develop/#230003247
   On 3.0, highlighting doesn't work

NOTE: The project told me two issues: other one #1385

Operating System and Browser

Windows 7 HomePremium 64bit SP1
Firefox 61.0.1

[joker314]

Note to anyone trying to do this:

• list monitors are rendered in LLK/scratch-gui
• the behaviour of 'flashing' is implemented in Add sprite target highlighter on sprite-tile click scratch-gui#3585 (though it deals with boxes around sprites rather than list indices), so it might be a useful reference for you

[towerofnix]

Note that you the highlighted item is also automatically scrolled to.

Also, while working with the linked project, do not click the list items; this prevents the "when key pressed" hat block from detecting input.