Add `getUrl` to `CorHttpd.js` to add compatibility with `@ionic-native/httpd` wrapper

[colossatr0n]

I've filed an issue with the Capacitor httpd wrapper repo since the wrapper Httpd class uses getUrl instead of getURL. This prevents the cordova-httpd plugin from loading in Ionic + Capacitor apps if added in the way that the Ionic doc shows.

In the meantime, getUrl can be added to CorHttpd.js.