Create Dockerfile for Billing (#2477)

* build script for billing

* Add entrypoint script

* Add dockerfile and docker ignore

src/Billing/Dockerfile

@@ -0,0 +1,21 @@
+FROM mcr.microsoft.com/dotnet/aspnet:6.0
+
+LABEL com.bitwarden.product="bitwarden"
+
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends \
+        gosu \
+        curl \
+    && rm -rf /var/lib/apt/lists/*
+
+ENV ASPNETCORE_URLS http://+:5000
+WORKDIR /app
+EXPOSE 5000
+COPY entrypoint.sh /
+RUN chmod +x /entrypoint.sh
+
+COPY obj/build-output/publish .
+
+HEALTHCHECK CMD curl -f http://localhost:5000/alive || exit 1
+
+ENTRYPOINT ["/entrypoint.sh"]