Added Dockerfile to build a docker image for building the app

Dockerfile

@@ -0,0 +1,23 @@
+# This Dockerfile was created merely to build the app through CI. It might work
+#   for local builds, but is not guaranteed.
+
+# build the app with Node.js version 16
+FROM node:16
+
+# set working directory of the build
+WORKDIR /usr/src/app
+
+# install dependencies
+RUN apt update && \
+    apt install -y ruby ruby-dev rpm \
+    gem install sass
+
+# make sure node_modules and public exist so we can ensure it's own by the right user
+RUN mkdir /usr/src/app/{node_modules,public}
+
+RUN chown -R node /usr/src/app
+
+USER node
+
+VOLUME /usr/src/app/node_modules
+VOLUME /usr/src/app/public