Per-site extension configuration seems to be completely broken

[theFisher86]

Description of the problem

When clicking on the icon and selecting "Allow Per-Site extension configuration" the checkbox doesn't "save." As soon as the dialog closes the check disappears. Additionally, going into settings and adding a site to the list to be disabled has no effect either.

Url of the page where the problem occurs (not the image url)

https://nomansskymods.com

Steps to reproduce the problem (include image url here)

1. Go to a VGMods site
2. Check the "Allow Per-Site extension configuration" box
3. Click anywhere else
4. Click the HoverZoom icon again
5. Box is no longer checked.

OS version, extension version (Chrome only, Firefox is not supported)

OS: Win10 Chrome: 68.0.3440.106 HoverZoom: 1.0.132