Add a Dockerfile, submitted by @Opvolger in #498.

If I understand this right it only builds the dedicated server. I think
that Dockerfiles need to be at the project root. Nevertheless I put it
under stuff/, the root dir is already cluttered enough.

Closes #498.

stuff/misc/Dockerfile

@@ -0,0 +1,28 @@
+FROM ubuntu:18.04 AS build
+
+WORKDIR /yquake2
+RUN apt-get update
+RUN apt-get install libcurl4-openssl-dev build-essential -y
+COPY . .
+
+RUN make server game
+
+FROM ubuntu:18.04 AS runtime
+
+ENV server_cfg="server.cfg"
+
+EXPOSE 27910
+
+# Add the user UID:1000, GID:1000, home at /yquake2
+RUN groupadd -r yquake2 -g 1000 && useradd -u 1000 -r -g yquake2 -m -d /yquake2 -s /sbin/nologin -c "yquake2 user" yquake2 && \
+    chmod 755 /yquake2
+
+WORKDIR /yquake2
+COPY --from=build /yquake2/release ./
+
+# Specify the user to execute all commands below
+USER yquake2
+
+RUN mkdir .yq2
+VOLUME ["/yquake2/.yq2"]
+ENTRYPOINT ./q2ded +exec ${server_cfg}