Added docker file to build custom worker

Author: Hanzhang Zeng (Roger)

CustomWorker.dockerfile

@@ -0,0 +1,19 @@
+FROM mcr.microsoft.com/azure-functions/python:3.0-python3.6
+
+RUN rm -rf /azure-functions-host/workers/python/3.6/LINUX/X64/azure_functions_worker
+
+COPY azure_functions_worker /azure-functions-host/workers/python/3.6/LINUX/X64/azure_functions_worker
+
+ENV AzureWebJobsScriptRoot=/home/site/wwwroot \
+    AzureFunctionsJobHost__Logging__Console__IsEnabled=true \
+    FUNCTIONS_WORKER_PROCESS_COUNT=1 \
+    PYTHON_THREADPOOL_THREAD_COUNT=1 \
+    FUNCTIONS_WORKER_RUNTIME_VERSION=3.6
+
+COPY requirements.txt /
+RUN pip install --upgrade pip
+RUN pip install -r /requirements.txt
+
+COPY . /home/site/wwwroot
+
+CMD [ "/azure-functions-host/Microsoft.Azure.WebJobs.Script.WebHost" ]