Fix #200 debian package

• Script to build deb packages using Docker.
• Build deb packages in GitLab CI.
• Two services (mirror and smith) for Duniter.
• A service and systemd timer for the distance oracle.
• Dev documentation to build deb packages.
• User documentation to install and run a node.

One hypothesis I made for the sake of simplifying user configuration is that the chain ID equals the chain name. This may not be valid for testing, but it is valid for live chains. This way, we can generate the oracle distance base path using the node and chain name paths.

docker/build-deb.Dockerfile

+FROM paritytech/ci-linux:production
+
+# Set the working directory
+WORKDIR /app/
+
+# Copy the toolchain
+COPY rust-toolchain.toml ./
+
+# Install toolchain, substrate and cargo-deb with cargo cache
+RUN --mount=type=cache,target=/root/.cargo \
+    cargo install cargo-deb
+
+# Create a dummy project to cache dependencies
+COPY Cargo.toml .
+COPY rust-toolchain.toml ./
+RUN --mount=type=cache,target=/app/target \
+    --mount=type=cache,target=/root/.cargo/registry \
+    mkdir src && \
+    sed -i '/git = \|version = /!d' Cargo.toml && \
+    sed -i 's/false/true/' Cargo.toml && \
+    sed -i '1s/^/\[package\]\nname\=\"Dummy\"\n\[dependencies\]\n/' Cargo.toml && \
+    echo "fn main() {}" > src/main.rs && \
+    cargo build -Zgit=shallow-deps --release && \
+    rm -rf src Cargo.lock Cargo.toml
+
+# Copy the entire project
+COPY . .
+
+# Build the project and create Debian packages
+RUN --mount=type=cache,target=/app/target \
+    --mount=type=cache,target=/root/.cargo/registry \
+    cargo build -Zgit=shallow-deps --release && \
+    cargo deb --no-build -p duniter && \
+    cp -r ./target/debian/ ./
+
+# Clean up unnecessary files to reduce image size
+RUN rm -rf /app/target/release /root/.cargo/registry