Modernize project targets and Docker test flow

Dockerfile

@@ -0,0 +1,15 @@
+FROM mcr.microsoft.com/dotnet/sdk:10.0 AS restore
+WORKDIR /src
+
+COPY VirtualFS.sln ./
+COPY VirtualFS/VirtualFS.csproj VirtualFS/
+COPY VirtualFS.Tests/VirtualFS.Tests.csproj VirtualFS.Tests/
+
+RUN dotnet restore VirtualFS.sln
+
+FROM restore AS build
+COPY . .
+RUN dotnet build VirtualFS.sln -c Release --no-restore
+
+FROM build AS test
+RUN dotnet test VirtualFS.Tests/VirtualFS.Tests.csproj -c Release --no-build