Why the extension requires reading browsing history permission?
The sole permission required by the extension is tabs, which gives accessing browser tabs information capability.
We use this permission to open the search result in the
current tab or
file: doc not work properly on Firefox?
For security reasons, in Firefox,
file: URLs is an unprivileged URL, accessing to those unprivileged URLs are prohibited.
See the MDN documentation for more detail.
Any workaround to support offline mode on Firefox?
Sure. A good choice is use http server! For example using python http.server module:
$ cd ~/Downloads/html-book-20200913/reference $ python -m http.server Serving HTTP on 0.0.0.0 port 8000 (http://0.0.0.0:8000/) ...
http://0.0.0.0:8000/en as your local doc path.