Insert vertical-space block (Javascript)
completed by: Scimonster
mentors: Sugar Labs
In Turtle Blocks, when a large argument block is inserted into the top slot of two-argument block, the block expands so that the lower argument is not obscured. However, then a large argument block is inserted into the bottom slot, the block below is obscured. This task is to detect large arguments inserted into the bottom slot and rather than further expand the block itself, insert a vertical-space block below the current block. (If there is already a vertical space block, don't insert a second one.)