(proposal) feat(semantic): add `ReferenceFlag::JSDoc`

Consider this code snippet:
```ts
import type { RelevantType } from './foo'

/**
 * @see {@link RelevantType}
 */
type OtherType = number
```
It would be nice if `no-unused-vars` did not report `RelevantType` as unused. Maybe we could mark this link as a usage?