Added Dockerfile for all languages

c#/Dockerfile

@@ -0,0 +1 @@
+FROM mcr.microsoft.com/dotnet/sdk:3.1

docker-compose.yaml

@@ -2,20 +2,20 @@ version: "3"
 services: 
   csharp:
     container_name: csharp # image name
-    image: <dockerhub account>/csharp_sdk:1.0.0
+    image: cruxlight/csharp_sdk:1.0.0
     build:
         context: ./c#
   golang:
     container_name: golang
-    image: <dockerhub account>/golang_sdk:1.0.0
+    image: cruxlight/golang_sdk:1.0.0
     build: ./golang
   nodejs:
     container_name: nodejs
-    image: <dockerhub account>/nodejs:1.0.0
+    image: cruxlight/nodejs:1.0.0
     build: ./nodejs
   python:
     container_name: python
-    image: <dockerhub account>/python:1.0.0
+    image: cruxlight/python:1.0.0
     build: ./python
   first-public-dockerhub-image:
     container_name: first-public-dockerhub-image

golang/Dockerfile

@@ -0,0 +1 @@
+FROM golang:1.12.5-alpine3.9 as builder

nodejs/Dockerfile

@@ -0,0 +1 @@
+FROM node:12.4.0-alpine

python/Dockerfile

@@ -0,0 +1 @@
+FROM python:3.7.3-alpine3.9