`ref` element type not inferred correctly

Hi, great library, thanks for creating it! I'm using it in [React Interactive](https://github.com/rafgraph/react-interactive)

Using the `Heading` `forwardRef` example in the readme the `ref` element type implicitly is `any`:
For a live reproduction see: https://codesandbox.io/s/polymorphic-inferred-ref-type-zqyl6
```ts
{}}
>
As h1

```

Note that when creating a props object to pass to `Heading` the `ref` element type is inferred correctly:
```ts
const propsForHeading: HeadingProps<"h1"> = {
// element type is inferred correctly
ref: (element) => {},
children: "Heading using propsForHeading"
};

...

```

Start with the Heading forwardRef example in the README and compare it with the linked CodeSandbox reproduction. Investigate why the inline ref callback loses the element type while a HeadingProps<"h1"> props object infers it correctly; done means the inline callback receives the appropriate h1 element type without an explicit annotation.

Written by the indexing model from the issue text.