send-to-spillo by jpr, Ed Mechem

This release overhauls the way send-to-spillo calls out to Spillo and does away with the creation of temporary Tabs 🎉.

When running send-to-spillo the first time Firefox pops up a request to explicitly let the user allow the extension to communicate with the Spillo native binary.
With the way things were built up to now this wasn't really working, because all of this would happen in a new Tab the extension opened and closed really fast. Users didn't really have any chance of approving this.

Trying to solve this problem, we've come up with a better solution for the overall way send-to-spillo works: Now we simply append an invisible link (invisible, because it contains no text), make the browser click it and invoke Spillo that way.
This also has the benefit, that the permissions dialog (if still shown) is presented in the context of the current tab, so the user can't really miss it.