Button doesn't load when navigating on GitHub

[Keith94]

It may be a bug or limitation in the WebExtensions API, but I wanted to report it just in case. ;)

Steps to reproduce

1. Navigate to https://github.com/shgysk8zer0/awesome-rss/issues
2. Click on one of the other tabs (e.g. Pull requests)

Expected behavior

RSS icon should(?) re-appear or stay visible in the url bar

Actual behavior

RSS icon disappears from url bar and requires reloading the page to appear again

[shgysk8zer0]

Confirmed. It also suffers from the same issue when navigating using the back/forward buttons.
In the case of the reported issue, the problem seems to be that the DOMContentLoaded event isn't triggered on fetch/XHR.