service/samples: add .dockerignore to samples with local build disruption risk

docs/serving/samples/hello-world/helloworld-csharp/.dockerignore

@@ -0,0 +1,4 @@
+Dockerfile
+README.md
+**/obj/
+**/bin/

docs/serving/samples/hello-world/helloworld-csharp/README.md

@@ -87,6 +87,15 @@ cd knative-docs/serving/samples/hello-world/helloworld-csharp
    CMD ["dotnet", "out/helloworld-csharp.dll"]
    ```
 
+1. Create a `.dockerignore` file to ensure that any files related to a local build do not affect the container that you build for deployment.
+
+   ```ignore
+   Dockerfile
+   README.md
+   **/obj/
+   **/bin/
+   ```
+
 1. Create a new file, `service.yaml` and copy the following service definition
    into the file. Make sure to replace `{username}` with your Docker Hub
    username.

docs/serving/samples/hello-world/helloworld-nodejs/.dockerignore

@@ -0,0 +1,4 @@
+Dockerfile
+README.md
+node_modules
+npm-debug.log

docs/serving/samples/hello-world/helloworld-nodejs/README.md

@@ -110,6 +110,15 @@ cd knative-docs/serving/samples/hello-world/helloworld-nodejs
    CMD [ "npm", "start" ]
    ```
 
+1. Create a `.dockerignore` file to ensure that any files related to a local build do not affect the container that you build for deployment.
+
+   ```ignore
+   Dockerfile
+   README.md
+   node_modules
+   npm-debug.log
+   ```
+
 1. Create a new file, `service.yaml` and copy the following service definition
    into the file. Make sure to replace `{username}` with your Docker Hub
    username.

docs/serving/samples/hello-world/helloworld-php/.dockerignore

@@ -0,0 +1,3 @@
+Dockerfile
+README.md
+vendor

docs/serving/samples/hello-world/helloworld-php/README.md

@@ -57,6 +57,14 @@ cd knative-docs/serving/samples/hello-world/helloworld-php
    RUN mv "$PHP_INI_DIR/php.ini-development" "$PHP_INI_DIR/php.ini"
    ```
 
+1. Create a `.dockerignore` file to ensure that any files related to a local build do not affect the container that you build for deployment.
+
+   ```ignore
+   Dockerfile
+   README.md
+   vendor
+   ```
+
 1. Create a new file, `service.yaml` and copy the following service definition
    into the file. Make sure to replace `{username}` with your Docker Hub
    username.

docs/serving/samples/hello-world/helloworld-python/.dockerignore

@@ -0,0 +1,6 @@
+Dockerfile
+README.md
+*.pyc
+*.pyo
+*.pyd
+__pycache__

docs/serving/samples/hello-world/helloworld-python/README.md

@@ -70,6 +70,17 @@ cd knative-docs/serving/samples/hello-world/helloworld-python
    CMD exec gunicorn --bind :$PORT --workers 1 --threads 8 app:app
    ```
 
+1. Create a `.dockerignore` file to ensure that any files related to a local build do not affect the container that you build for deployment.
+
+   ```ignore
+   Dockerfile
+   README.md
+   *.pyc
+   *.pyo
+   *.pyd
+   __pycache__
+   ```
+
 1. Create a new file, `service.yaml` and copy the following service definition
    into the file. Make sure to replace `{username}` with your Docker Hub
    username.