bookmark stack - web extension to save pages in a stack for reading them later

Available for Firefox here: https://addons.mozilla.org/firefox/addon/bookmark-stack/

This extension is heavily inspired by [view later](https://chrome.google.com/webstore/detail/view-later-save-links-in/hnolaplfoobcmgfmjphkmbjolinelpkb)
and [reading-list](https://addons.mozilla.org/firefox/addon/reading_list/)
but much simpler. For example, a simple bookmarks folder is used for storage.