Custom attribute syntax

[MendyBerger]

I'd like to be able to have custom syntax for attribute keys, to support syntax similar to Angular or Lit:

Angular:

<div  [prop]="foo"  (click)="callback"  [(twoWayBinding)]="bar">

Lit:

<div  .prop="foo"  @click="callback"  ?boolAttibute="biz">

Maybe something similar to transform_block but for attributes.

If this looks like a good idea to you, I might be able to create a PR.