Merge branch 'fix/public-key-warnings' into 'master'

Add `:public_key` to `extra_applications`

See merge request pleroma/elixir-libraries/http_signatures!1

mix.exs

@@ -18,7 +18,7 @@ defmodule HttpSignatures.MixProject do
   # Run "mix help compile.app" to learn about applications.
   def application do
     [
-      extra_applications: [:logger]
+      extra_applications: [:logger, :public_key]
     ]
   end