Export a generic list of html elements

## Proposal
Export a generic HTMLIntrinsics type, in addition to JSXIntrinsics.
[Line 271](https://github.com/facebook/flow/blob/v0.104.0/lib/react-dom.js#L271) removes the ability to verify a string is a valid html element

## Use case
For example:
```
const generateComponent = (ComponentString: $Keys<$JSXIntrinsics>, styleObject) => {
return
}

const ValidComponent = generateComponent('div'); // Works
const ShouldThrowErrorComponent = generateComponent('divv'); // Works! but it should fail
```

Without disrupting the existing behavior of JSXIntrinsics, we could add HTMLIntrinsics.