Legacy add-on seen in https://addons.mozilla.org/en-US/firefox/addon/tails-download-and-verify/
Enquiry added in Tails support seeking WebExtensions info https://labs.riseup.net/code/issues/14960
I think the current best approach for TAILS download is to follow the instructions on the website. And probably we need to give it visibility when asked as many people don’t even know tails.