Enable newer JavaScript syntax

Currently, we are a bit behind the browser implementations, which seems wrong to me.

E.g. the following code can be parsed and executed in Blink DevTools but not in a workspace.

```JavaScript
class Timer2 {
start = Date.now();
current = Date.now();

tick() {
this.current = Date.now();
}
}
```

I think we should come up with some future-prove solution here: How to do this knowing never syntax extensions wont stop coming?

The issue names no files or tests; start by locating the workspace's JavaScript parsing and execution entry points, then reproduce the provided class-field example and compare it with Blink DevTools. Done means the example works in a workspace and the project has a future-proof approach for newer syntax extensions.

Written by the indexing model from the issue text.