SVG MB logo, more HTTPS + small changes

[Schweinepriester]

Noticed the MB logo doesn't look so nice, e.g. on https://heilung.bandcamp.com/album/drif:

I've tried hard to find the logo somewhere hosted on https://musicbrainz.org/, but haven't succeeded. @zas, maybe you know? :)

So for now the new URL is not as nice: https://raw.githubusercontent.com/metabrainz/design-system/master/brand/logos/MusicBrainz/SVG/MusicBrainz_logo_icon.svg But as you probably guess from the URL, it's from the official design system here: https://github.com/metabrainz/design-system/blob/master/brand/logos/MusicBrainz/SVG/MusicBrainz_logo_icon.svg

And now it looks nice:

Additionally did a bit of stuff around.

In case you are wondering why I removed the protocol-relative URLs: https://www.paulirish.com/2010/the-protocol-relative-url/

Now that SSL is encouraged for everyone and doesn't have performance concerns, this technique is now an anti-pattern. If the asset you need is available on SSL, then always use the https:// asset.

Please test thoroughly before merging as I haven't 🙏