Firefox support

[Brugman]

Hi. Just tried the plugin. Love it!

It doesn't seem to work on Firefox Dev Edition 112, but it does work on Chrome. Is that just me or something that needs fixing?

[Brugman]

https://bugzilla.mozilla.org/show_bug.cgi?id=1689730

It seems to be an HTTP related bug in Firefox. It works on a production site. I guess this is beyond our control.