Yoyogames has released the source code for the HTML5 runner (i.e. all features and so on). I wonder if Enigma-Dev should not support it (or LateralGM / RadialGM) as one of the options. It seems to me that there is no GML to JS converter, so such code would have to be created, but the rest could be done.

But that's for someone to decide if it makes sense and implement :)

https://github.com/YoYoGames/GameMaker-HTML5