Add Dotnet 2.1, 3.1, 5.0 Docker Images (#9)

* Add Dotnet 2.1, 3.2, 5.0 Docker Images

dotnet/entrypoint.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+cd /home/container
+
+# Make internal Docker IP address available to processes.
+export INTERNAL_IP=`ip route get 1 | awk '{print $NF;exit}'`
+
+# Replace Startup Variables
+MODIFIED_STARTUP=$(echo -e ${STARTUP} | sed -e 's/{{/${/g' -e 's/}}/}/g')
+echo -e ":/home/container$ ${MODIFIED_STARTUP}"
+
+# Run the Server
+eval ${MODIFIED_STARTUP}