I did this with Blockly in Reeborg's World [1]; I added it many years ago. What would be the advantage of using BlockMirror over Blockly? Does it support translation?
If by "translation" you mean Mutual Language Translation (turns text into blocks, and blocks back into text, as you type/drag blocks) then yes. If you mean "translation between human languages" then less so. It supports whatever you can do with Blockly, minus whatever things I broke adding the MLT support. I'd love a PR to handle other languages, but again... time.