Related issues:
- https://github.com/uBlockOrigin/uBOL-issues/issues/5#issuecomment-1575425913
- https://github.com/w3c/webextensions/issues/403
Currently, there is no other way to inject CSS user styles than to
wake up the service worker, so that it can inject the CSS styles
itself using the `scripting.insertCSS()` method.
If ever the MV3 API supports injecting CSS user styles directly
from a content script, uBOL will be back to be fully declarative.
At this point the service worker is very lightweight since the
filtering is completely declarative, so this is not too much of
an issue performance-wise except for the fact that waking up the
service worker for the sole purpose of injecting CSS user styles
and nothing else introduces a pointless overhead.
Hopefully the MV3 API will mature to address such inefficiency.
