refactor: move app-release-template to monorepo

frontend/app-release-template/Dockerfile

@@ -0,0 +1,21 @@
+FROM registry.gitlab.com/openstapps/app
+
+ENV LC_ALL=en_US.UTF-8 \
+    LANG=en_US.UTF-8
+
+ENV TZ=Europe/Berlin
+RUN ln -snf /usr/share/zoneinfo/$TZ /etc/localtime && echo $TZ > /etc/timezone
+
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends \
+    xmlstarlet \
+    ruby-full \
+    zip \
+    openssh-client
+
+RUN gem install bundler
+
+COPY . /build
+WORKDIR /build
+
+RUN bundler update