新增learn-kubernetes（https://github.com/yyong-brs/learn-kubernetes）相关文件

learn/learn-kubernetes-master/kiamol/ch03/docker-images/numbers/numbers-web/Dockerfile

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+FROM mcr.microsoft.com/dotnet/sdk:6.0-alpine AS builder
+
+WORKDIR /src
+COPY src/Numbers.Web/Numbers.Web.csproj .
+RUN dotnet restore
+
+COPY src/Numbers.Web/ .
+RUN dotnet publish -c Release -o /out Numbers.Web.csproj
+
+# app image
+FROM mcr.microsoft.com/dotnet/aspnet:6.0-alpine
+
+ENV RngApi__Url=http://numbers-api/sixeyed/kiamol/master/ch03/numbers/rng \
+    RngApi__RetryHost=raw.githubusercontent.com
+
+ENTRYPOINT ["dotnet", "/app/Numbers.Web.dll"]
+
+WORKDIR /app
+COPY --from=builder /out/ .