favicon.ico being served is not dependent on Elixir's configuration, but
on the front-facing server. Its config must be updated to serve the
favicon; this is why favicon.ico used to not be commited into the
repo.
Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
Backwards compatibility for browsers without svg support (in this
version) causes the logo to unnecessarily flicker on navigation.
According to caniuse.com SVG in img elements is supported in browsers
used by 97.85% of users. https://caniuse.com/svg-img
Firefox introduced support in 2011, Chrome in 2013, Safari in 2015.
