Implement referrerPolicy IDL attribute for HTMLScriptElement and HTMLLinkElement

[jdm]

Spec:

• https://html.spec.whatwg.org/multipage/scripting.html#dom-script-referrerpolicy
• https://html.spec.whatwg.org/multipage/semantics.html#dom-link-referrerpolicy

[nosark]

I would like to work on this issue please

[jdm]

@nosark Great! This will require updating the webidl files for both interfaces to add the missing IDL attribute, then implementing the getters and setters for both HTMLScriptElement and HTMLLinkElement. For the getters you will want to extract the first few lines of referrer_policy_for_element into a helper function, and the setters can use the make_setter! macro like any other string-reflecting attribute. Finally, code like this for each element should call referrer_policy_for_element so that the proper values are used.

[nosark]

@jdm Okay, awesome! Thank you!