Mark as read doesn't work

[gabrielecirulli]

Steps to reproduce this issue

1. Enable the mark as read extension
2. Grant permissions (works on https://github.com/gabrielecirulli/hn-special/pull/103)
3. Apply
4. Use the mark as read button

Expected result

Links are added to the history and thus marked as read

Actual result

Links don't appear to be marked as read

Notes and screenshots

Using the dark theme it becomes clear that the color of the link is not changing to signal it's being marked as read or not.