Fix Docker setup and add back back an entrypoint

* Also add special deps for argon2 support inside the Alpine image
* Make sure yarn install is triggered

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

Dockerfile

@@ -1,11 +1,10 @@
 FROM bitwalker/alpine-elixir:latest
 
 RUN apk add inotify-tools postgresql-client yarn
+RUN apk add --no-cache make gcc libc-dev
 
 RUN mix local.hex --force && mix local.rebar --force
 
-COPY docker/entrypoint.sh /bin/entrypoint
-
 WORKDIR /app
 
 EXPOSE 4000 4001 4002