Broken links in README.md

[thaggie]

Thanks for creating / curating these resources, poking around I found that a few of the links are broken as they miss https:// from the front.

A few of the links are broken since they miss out the scheme from the URL.

1. Øystein Moseng's "Highcharts" link.
2. Sarah Fossheim's "Sarah Fossheim's Website" link.
3. Amy Cesal's "Amy's Website" link.