feat(backend): add initial backend

Backend as is can query GitHub for the information that will be
necessary later on in the frontend's pages. It does not cache this
information yet though.

Signed-off-by: Lucien Cartier-Tilet <lucien@phundrak.com>

Dockerfile

@@ -0,0 +1,12 @@
+FROM rust:alpine
+
+WORKDIR /app
+
+COPY Cargo.toml /app/Cargo.toml
+COPY Cargo.lock  /app/Cargo.lock
+COPY src /app/src
+
+RUN cargo build --release
+RUN cargo install --path .
+
+ENTRYPOINT [ "phuncache" ]