`install()` function should support the `monitor` option to report on language pack download progress

The [`install()`](https://webaudio.github.io/web-speech-api/#dom-speechrecognition-install) function doesn't report on language pack download progress. This should be possible to add following the [`CreateMonitorCallback`](https://webmachinelearning.github.io/writing-assistance-apis/#callbackdef-createmonitorcallback) `monitor` pattern.