Manifest v3 support

[KSR-Yasuda]

Do you have any plan to support extension manifest v3?
Otherwise, it is going to be removed from the web store.

[ffapd1989]

Please! It's very important for me too!

[spiegelm]

@blanch0t was so nice to create a pull request for this: #74
I hope the PR will be accepted soon. Thank you for the great work!

[blanch0t]

While it's not merged, you can clone my repo and upload the code directly to your chrome extensions

[mscheper]

@rogershen: It seems the work required to keep this extension alive has already been done. I use it a lot, so I hope you'll check the pull requrest.