Corrupted extension message

There's an issue with Chrome 63+ that claims the extension is corrupted.

I found a quick fix, just add the following line into the manifest.json
`
"update_url": "https://raw.githubusercontent.com/Cortys/comic-backup/master"
`
(it actually doesn't matter what URL is there, apparently). Don't forget to add the comma to the end of the line above if you put this at the end.