Fixes logos in darkmode

[madsrh]

Releated to #70
Added a mediaquery for darkmode to the SVG files. Sadly I wasn't able to test this 🙈 🤞

I couldn't find any guidelines for the Devuan logo, so I'm not sure if it looks better in black or perhaps with a subtle stroke.

[jpnurmi]

Awesome, thanks! 🤩 Unfortunately, the flutter_svg library doesn't support <style> elements but we could have separate files with dark variants. I'll take a look!

════════ Exception caught by SVG ═══════════════════════════════════════════════
The following UnimplementedError was thrown in parseSvgElement:
The <style> element is not implemented in this library.

Style elements are not supported by this library and the requested SVG may not render as intended.

[jpnurmi]

Thank you, @madsrh! This is a huge improvement :)

os-logos.webm