add progressive support for showSaveFilePicker #5
Description
Firefox & Safari still don't support the File Access API - we're interested in showSaveFilePicker
Using something like: https://github.com/jimmywarting/native-file-system-adapter provides is a polyfill with a safe fallback to achors. So it will still be a dumb download anchor on Firefox and Safari, but Chrome variants will provide a native "Save Dialog".
Issues which this would bring about:
- Unit tests will be challenging with native browser dialogs we can't interact with
- It would be cool to have "Save" and "Save-As" (almost the same, but gives a better UX), however, given this is progressive, save-as will not always be save-as. Need to consider this.