feat: add dockerfile to make fetch system deps

Dockerfile

@@ -0,0 +1,10 @@
+FROM elixir:1.15.7-slim AS builder
+
+RUN apt-get update \
+  && apt-get -y install make
+
+WORKDIR /opt/app
+COPY ./mix.exs ./
+COPY ./mix.lock ./
+RUN mix do local.hex --force, local.rebar --force \
+  && mix do deps.get, deps.compile

docker-compose.yml

@@ -13,7 +13,10 @@ services:
       - 'db_data:/var/lib/postgresql/data'
     restart: unless-stopped
   app:
-    image: 'elixir:1.15.7-slim'
+    image: &app_image 'joaodubas/ex_trainer:${EX_TRAINER_TAG:-dev}'
+    build:
+      target: builder
+      context: .
     hostname: app
     depends_on:
       - db