SVP support + 2 bugfixes

[Henri-J-Norden]

With the youtube-dl configuration SVP uses, path contains the direct googlevideo.com url, while the youtube video link with the video ID is in http-header-fields. This adds another pattern match to check if this is the case.

Additional changes:

• sponsorblock.py was using exit instead of sys.exit which generated an unhandled exception on DB update failure
• OSD message now displays the category of the skipped segment, not just 'sponsor'
• Added some debugging messages to mpv's log file

[Henri-J-Norden]

Thanks for the review, I think these points should be solved now!