Adds a button to the browser that opens the current web page in the AIID submission form.
To build:
npm run build
This will create build/chromium/, build/firefox/, and build/aiid-widget-web-ext.zip. The first of these can be loaded as an unpacked extension in chromium-derived browsers, and the latter two can be loaded as temporary add-on in Firefox.
Tests can be run with
npm run test
Currently this will test that the extension loads correctly in Chromium.