add docker setup

Dockerfile

@@ -0,0 +1,45 @@
+FROM ruby:3.1.1-alpine
+
+ENV APP_PATH /posterr/
+ENV APP_USER posterr
+ENV APP_USER_HOME /home/posterr
+
+ENV BUNDLE_PATH $APP_USER_HOME
+ENV GEM_HOME $APP_USER_HOME/bundle
+ENV BUNDLE_BIN $GEM_HOME/bin
+
+ENV RAILS_LOG_TO_STDOUT=true
+ENV TZ=America/Sao_Paulo
+
+ENV PATH $PATH:$BUNDLE_BIN
+
+# Puma
+EXPOSE 3000
+
+ARG UID
+RUN : "${UID:?You must provide a UID argument when building this image.}"
+
+RUN adduser -h $APP_USER_HOME -D -u $UID $APP_USER
+
+WORKDIR $APP_PATH
+
+COPY Gemfile* $APP_PATH
+
+# The package shared-mime-info is required in a Rails dependency
+RUN apk update && \
+  apk add --no-cache \
+    git \
+    build-base \
+    postgresql-dev \
+    tzdata \
+    less \
+    shared-mime-info && \
+  bundle config jobs $(nproc --all) && \
+  bundle install && \
+  chown -R $APP_USER:$APP_USER $APP_USER_HOME && \
+  chown -R $APP_USER:$APP_USER $APP_PATH && \
+  rm -r /var/cache/apk/*
+
+COPY --chown=posterr . $APP_PATH
+
+USER $APP_USER