Brotli library revival and support for Phoenix 1.6 assets digests

[hauleth]

This library became deprecated in favour of phoenix_bakery which provides the same features + better GZIP and Zstandard

PhoenixBakery - better compression for your Phoenix assets

PhoenixBakery is library for Phoenix 1.6 (and later) that provides modules implementing Phoenix.Digester.Compressor. There are currently 3 modules: PhoenixBakery.Gzip that replaces default Phoenix.Digester.Gzip with stronger compression at cost of run time and memory usage. But as it is one-time action (for each release) it is IMHO better to use that build time for less transfer used later PhoenixBakery.Brotli that provides support for Brotli algorithm designed by Google and currently suppor…