Point spec link to official Ecma specification

[jkup]

Hello!

I was curious if there was any interest in pointing the "Spec" link on http://sourcemaps.info/ to the official Ecma specification? We standardized sourcemaps under Ecma International at the end of last year and are continuing to do exciting feature work over at https://tc39.es/ecma426/. You can see the work in progress here: https://github.com/tc39/ecma426

Would love to have this website point to that work if possible!