transformer: missing initializer for TypeScript class constructor when argument is readonly

### In
```ts
class Boo {
  constructor(
    readonly prop: number = 0
  ) {}
}
```

### Out

```ts
class Boo {
    constructor(prop = 0) {}
}
```

### Expected

```ts
class Boo {
    constructor(prop = 0) {
        this.prop = prop;
    }
}
```