Attribute Transformers

Initial discussion at https://github.com/forgojs/forgo/issues/54

Parts of the discussion are copied below for context:

### Initial proposal by @spiffytech

Forgo could allow libraries to implement this if component had a method to modify attributes before they're put onto the DOM. Something like:

```tsx
function someFunc() {
transformAttr(name, value, args) {
if (name.startsWith('on')) {
return autoRedraw(value, args);
}
return value;
},
render() {...}
}
```

Then you could imagine a library exposing this the same way forgo-state accepts a component and returns a component with modified lifecycle methods.

Pair this with wanting click handlers to run inside the component's error boundary and we've got two examples where modifying DOM node attributes is useful.