Add arm64v8 dockerfile

arm64v8.dockerfile

@@ -0,0 +1,18 @@
+FROM mcr.microsoft.com/dotnet/core/sdk:3.1-buster-arm64v8 AS build
+WORKDIR /app
+
+# Separate layers here to avoid redoing dependencies on code change.
+COPY *.sln .
+COPY *.csproj .
+RUN dotnet restore
+
+# Now the code.
+COPY . .
+RUN dotnet publish -r linux-musl-arm64 -c Release -o out
+
+FROM mcr.microsoft.com/dotnet/core/runtime-deps:3.1-alpine-arm64v8 AS runtime
+WORKDIR /app
+COPY --from=build /app/out .
+
+ENTRYPOINT ["./docker_exporter"]
+