added docker file in workflows

Author: {ravi kumar bulusu}

.github/workflows/Dockerfile

@@ -0,0 +1,18 @@
+FROM mcr.microsoft.com/dotnet/sdk:8.0 AS build-env
+WORKDIR /app
+
+# Copy csproj and restore as distinct layers
+COPY *.csproj ./
+RUN dotnet restore
+
+# Copy everything else and build
+COPY . ./
+RUN dotnet publish -c Release -o out
+
+# Build runtime image
+FROM mcr.microsoft.com/dotnet/aspnet:8.0
+WORKDIR /app
+COPY --from=build-env /app/out .
+# Default ASP.NET port changed with .NET 8.0
+ENV ASPNETCORE_HTTP_PORTS=80
+ENTRYPOINT ["dotnet", "RazorPagesTestSample.dll"]