thunderbird/webext-examples — reverse-engineered prompt

Build me a small public repo of working Thunderbird WebExtension example add ons that people can learn from and run locally. I want a simple Hello World tutorial example, plus a collection of tiny samples that show common Thunderbird add on jobs like reading address books, changing compose message content, reacting when a message is displayed, adding menu items and toolbar buttons, using storage, working with IndexedDB, previewing PDF or image attachments, filtering messages, and asking for confirmation before sending.

Please include versions for Manifest V2 and Manifest V3 where that makes sense, and add clear comments in the Manifest V3 examples so someone can see what changed. Keep each example small and focused, with its own manifest at the top of the example folder. Add a friendly README that lists what every sample does and explains how to load an example as a temporary add on in Thunderbird or zip it for install. Look up current Thunderbird add on docs online if needed.