Changing github.com/vanadium/docs/blob/master links to vanadium.github.io
Changing github.com/vanadium/docs/blob/master links to vanadium.github.io

Change-Id: I9999dc110b7b55631bc25dac0851dc440179fb72

vanadium/playground,vanadium/playground,vanadium/playground,vanadium/playground