Extension: Compatibility with Safari / Edge / Opera

Since adding support for other browsers means more time spent on testing, debugging and deploying, we'll let the community handle this one. If you want the extension to work in one of the following browsers test it, make pull requests if necessary and we'll handle the deployment.

# Opera
Supports WebExtensions this should be pretty easy.

# Edge
Partially support WebExtensions, may need additional developments to work

# Safari
Does not support WebExtensions. Needs a full re-implementation.

# Yandex

# Vivaldi

--------------------

See https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Browser_support_for_JavaScript_APIs for details about compatibility.

No repository files or tests are named. Start by reviewing the linked MDN browser-compatibility reference and testing the extension in one target browser, beginning with Opera or Edge as described. Done means the extension works in the selected browser and any necessary changes are submitted as a pull request; deployment is handled by the maintainers.

Written by the indexing model from the issue text.