fix: when clearing a list, only close the popup if all other lists are also empty

fix: check that regex options are loaded before using

add options for custom regex patterns

for each media type, there are 2 new options:
1. override
- if checked:
then the default regex pattern for this media type is not used
- if unchecked:
then both the default regex pattern and custom pattern are used
2. pattern
- a custom regex pattern that is tested against every URL request
- empty values are ignored

* add ability to pin visibility of the top header with toggle
* add ability to expand visibility of full URLs with toggle

Add ability to manually select external website.

The 'Automatic' option is default, and uses the extension options to choose the most appropriate value, which is identical to the previous behavior.

add workaround for a HUGE bug in Firefox desktop Private Browsing mode

https://bugzil.la/1329304