Yandex.Translate add-on for removing newline characters from the clipboard and then inserting the clipboard into the input window by pressing F5.
Based on Your first extension.
Checking the performance of the add-on was carried out in Firefox Browser Developer Edition.
Firefox versions Extended Support Release (ESR), Developer Edition and Nightly will allow you to bypass the add-on signing requirement if you change the parameter xpinstall.signatures.required to false in the Firefox configuration editor (about:config page).
Or you can sign add-on yourself.
To install add-on create .zip file with the repository files(repository .zip file downloading throws error, create .zip file which does not contain exclusively folder carriage-eater-main) and drop it to about:addons page.