Add dockerfile to facilitate build on any platform (#97)

* Add dockerfile to facilitate build on any platform

* Polish up dockerfile

* Just a little more polish

Dockerfile

@@ -0,0 +1,18 @@
+FROM mono:6.12.0
+
+# Install .NET SDK
+ENV DOTNET_VERSION=5.0
+
+RUN curl -sSL https://dot.net/v1/dotnet-install.sh  \
+    | bash -s -- -Channel $DOTNET_VERSION -InstallDir /usr/share/dotnet \
+    && ln -s /usr/share/dotnet/dotnet /usr/bin/dotnet
+
+WORKDIR /build
+
+CMD [ "dotnet", "build" ]
+
+## Build Docker image (one time):
+# docker build -t shc-build . --no-cache
+
+## Build solution (every time):
+# docker run --rm -v .:/build shc-build