Missing fetchPriority property in HTMLLinkElement, HTMLImageElement and HTMLScriptElement

[Dagur]

Missing/Incorrect APIs

HTMLLinkElement, HTMLImageElement and HTMLScriptElement don't have the fetchPriority property yet.

Relevant documentation

https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Attributes/fetchpriority

[SamChou19815]

Should be filed in https://github.com/flow-typed/flow-typed/issues