Link checking using XHR.
Quick and dirty checking of links in page using XHR.
Failed links are dumped in the console.
Green links returned status code in range [200, 400)
Red links returned error code.
Blue links timed out or there was some error sending the HTTP request.
HTTP HEAD is tried first, then GET.
Icon image: Wikimedia External link icon rasterized from SVG.
1.3.0 - Update to manifest version 2 away from deprecated version 1
1.2.1 - Added clearing feature