Warning:
It's a big security risk to run browser extensions that you don't trust.
They can silently read and change webpages that you go to.
I highly recommend you read all of the code in the extension before installing.
Download here: extension.zip
Chrome Instructions: https://developer.chrome.com/docs/extensions/get-started/tutorial/hello-world#load-unpacked.
Firefox Instructions: https://extensionworkshop.com/documentation/develop/temporary-installation-in-firefox/