Browser logos are broken on README

[mkxml]

Hey guys,

I noticed that the browser support logos are not showing properly on README.

It looks like alrra/browser-logos switched the location of the image files to another directory, they are located inside a src folder now.

Also, since the repo was using PNG logos we could take the opportunity to switch to SVG ones (they look better on HiDPI displays).

I could put up a PR for this if wanted.

Thanks!

[fdaciuk]

Hey @mkxml! Feel free to send a PR =)