percy: capture images with base64 converted src
Created by: gitstart-sourcegraph
Description
Percy doesn't take screenshots of page at the time calling percySnapshot but captures DOM, CSS rules and uses them to render pages on their browsers including fetching assets, at that points, image src values still have the domain for testing, so Percy won't be able to capture them.
In this PR fixes that issue with converting all img src to base64 uri before calling percySnapshot