Add Docker build

Dockerfile

@@ -0,0 +1,15 @@
+FROM debian:12-slim
+
+# set work directory
+WORKDIR /usr/src/app
+
+# Print output
+RUN export TERM=xterm
+
+# install software
+RUN apt update
+RUN apt install -y emacs-nox
+
+# Build
+COPY build.el .
+ENTRYPOINT emacs --batch --script build.el