Add Dockerfile and CI workflow for Bevy headless (#38)

Dockerfile

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+FROM ubuntu:jammy
+# as rust-base
+
+# NB: This can be "stable" or another version.
+ARG RUST_TOOLCHAIN="1.75.0"
+
+WORKDIR /tmp
+
+# NB: cmake is required for freetype-sys-0.13.1, which in turn has only been added for egui.
+# NB: fontconfig is required by servo-fontconfig-sys, which is in the dependency chain for egui.
+# NB: libfontconfig-dev is required by servo-fontconfig-sys, which is in the dependency chain for egui.
+# NB: pkg-config and libssl are for container TLS; we may switch to rustls in the future.
+# BEVY SPECIFIC -
+# NB: libasound2-dev for alsa-sys
+# NB: libudev-dev for libudev-sys
+RUN apt-get update \
+    && DEBIAN_FRONTEND=noninteractive TZ=Etc/UTC apt-get install -y \
+        build-essential \
+        cmake \
+        libasound2-dev \
+        libudev-dev \
+        curl \
+        fontconfig \
+        libfontconfig1-dev \
+        libssl-dev \
+        pkg-config
+
+# Install Rust
+RUN curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs \
+    | sh  -s -- --default-toolchain $RUST_TOOLCHAIN -y
+
+# Report Rust version for build debugging
+RUN $HOME/.cargo/bin/rustup show
+RUN $HOME/.cargo/bin/rustc --version
+RUN $HOME/.cargo/bin/cargo --version
+
+# Install NPM
+# https://nodejs.org/en
+# https://github.com/nodesource/distributions
+#RUN curl -fsSL https://deb.nodesource.com/setup_21.x | bash - && \
+#  apt-get install -y nodejs
+
+# NB: Now we build and test our code.
+COPY Cargo.lock .
+COPY Cargo.toml .
+COPY ./ .
+
+
+RUN LD_LIBRARY_PATH=/usr/lib:${LD_LIBRARY_PATH} \
+  $HOME/.cargo/bin/cargo build \
+  --release \
+  --bin studio-headless