add elem.shadowRoot fallback in getShadowRoot

[ryanbr]

Unable to create a PR on https://github.com/gorhill/uBlock From @antonok-edm cc: @gorhill

const getShadowRoot = elem => {
        // Firefox
        if ( elem.openOrClosedShadowRoot ) {
            return elem.openOrClosedShadowRoot;
        }
        // Chromium
        if ( typeof chrome === 'object' ) {
            if ( chrome.dom && chrome.dom.openOrClosedShadowRoot ) {
                return chrome.dom.openOrClosedShadowRoot(elem);
            }
        }
-        return null;
+       return elem.shadowRoot;
    };

[antonok-edm]

(in commit form)

This should make the function slightly useful when running in non-extension contexts (where it currently identifies nothing). It won't be able to identify closed shadow roots, but only open is still an improvement.

Brave on Android/Desktop will get isolated world support, but it's currently unclear if/how that can be done for iOS given WebKit API constraints so it may be stuck with this solution for a while.

[gorhill]

Merged from your repo: gorhill/uBlock@c8b42ea