Motivation: looked into this it as part of #3687 (#3690)
Explanation: `Object.create(null)` returns value of `any` type.
So bellow construct is not reported by TS even in "strict" mode:
```ts
const foo = Object.create(null);
```
Fixing this issue in `extendSchema` requires adding more code since we
can't put all extensions nodes into one collection without loosing
typesafety.
