I'm wary of installing an extension that can access my data in gmail. Is the source code available anywhere?

Edit1: Found a chrome extension that lets me view the source code of chrome extensions[1]

Edit2: The inclusion of bootstrap.css is changing the appearance of some things, namely the "show original" message view. It also doesn't seem to detect the tracking image included by yesware

Edit3: Could I break this by adding "safe-img" somewhere in my tracking pixel url?

[1] https://chrome.google.com/webstore/detail/chrome-extension-s...