HTML A-frame add onclick function to a shader

[Aidan]

Hello, I have some code written in a-frame (https://aframe.io) that can be found at https://jsfiddle.net/AidanYoung/h0cb1nq8/
And I'm trying to find a way to add an onclick event to the

 <a-entity id="lettersEntity"  onclick='console.log("Hello")' geometry="primitive: plane; width: 2; height: 2" rotation="-30 -30 0" position="-0.2 1.5 -2.5" material="shader: html; target: #target; transparent: true; ratio: width; fps: 1.5"></a-entity>

part of my code. I haven't been able to find a way to make it so when I click on the object a function is triggered. I have tried adding a simple onclick function to the html element but I've been unsuccessfull. Does anybody know how I can add an onclick function to the element above?

[1]: https://jsfiddle.net/AidanYoung/h0cb1nq8/