Filter blacklist Implementation

First pass proposal for filter implementation. This is in relation to https://github.com/Moon-0xff/gnome-mpris-label/issues/4#issue-1463356957

Note that I am only doing a blacklist filtering here. I am not sure why we might require a white list?

The implementation should be self-explanatory but basically, I tried to keep it as simple and robust as possible by simply checking if the source_name is somewhere in the blacklist. I tested this and it worked fine. I can't really think of any case which would create "false positives". The added benefit is that if the user takes some freedom on the syntax, adding spaces or using semicolons (or any other separator), it would still work since the SOURCES_BLACKLIST syntax which is the one the user enters manually doesn't matter much.

The only small thing I noticed is that if the currently playing source is blacklisted by a user, it won't disappear right away which would be neat. It will have to wait until the source is changed manually/automatically or the extension reloaded. Once it's flushed out, it won't come back. It's a bit of an edge case but I just wanted to point it out in case you notice it too. I had a quick look to see if I could address this quickly but I didn't really want to start updating extension.js as this could start introducing some unintended regressions.

Let me know if you want me to update the merge request to be against main rather than filter-list.

PS: obviously, all chromium based browsers will end up being filtered as the same time but that's kind of inevitable

Moon-0xff / gnome-mpris-label

Filter blacklist Implementation #18