Hmm, this is very neat and elegant! But how well is svg (or data:) favicons supported in random non-strictly-browser context, like password managers, or some link aggregator/bookmarking style sites or apps?
You can check the browser supports on https://caniuse.com/link-icon-svg
You can download the PNG version to create favicon for older browsers, but it's something we'll cover in the next version. There would be a "Download All" option with all required PNG sizes, and a sample html file with higher priority for the SVG version. So modern browsers would use the SVG version, and old browsers uses the PNG files.