Add files for creating docker image

* Base on a small node image (alpine-node)
* Exclude some files from docker build to make the build go faster

.dockerignore

@@ -0,0 +1,5 @@
+.git
+docker-compose.yml
+node_modules
+artifact.json
+finnbuild.json

Dockerfile

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+FROM mhart/alpine-node:0.10.38
+
+COPY . .
+
+RUN npm install --production && \
+    npm run build
+
+EXPOSE 4242
+ENTRYPOINT ["npm"]
+
+CMD ["start"]