Disallow setting innerHTML inside the constructor

[stramel]

As @bennypowers points out in his tweet, https://twitter.com/PowersBenny/status/1383706876106395648

It can be detrimental to performance to set innerHTML inside the constructor. To accomplish this in a more performant way, you can create a static template and append that to the shadow dom instead.

This would be a fairly easy rule to detect and provide guidance for better perf.