Docs suggestion: use icon for current page favicon

[coliff]

Could be neat to use the current icon as the SVG favicon. Useful if you have lots of tabs open.

The code I used for the above quick test was adding this to the favicons.html partial:

{{ if not .IsHome }}
<link rel="icon" href="/assets/icons/ {{- .Title | urlize -}}.svg" sizes="all" type="image/svg+xml">
{{ end }}

but it needs a bit more work - right now the favicon.ico is loading instead. I think <link rel="icon" href="/assets/img/favicons/favicon.ico"> can be safely removed anyway if there is a favicon.ico in the sites root.

I like the idea of implementing this but there are a few things to note/potential issues.

• The icon appears black so doesn't look great with dark themes. could potentially use media query on the icon and CSS to invert it or something?
• Safari doesn't support SVG favicons still :-( (but will fallback to Bootstrap 'B' icon PNG.