small update to contrig. guide page

Dockerfile

@@ -0,0 +1,5 @@
+FROM nginx
+
+COPY . /usr/share/nginx/html
+
+EXPOSE 80

docker-compose.yml

@@ -0,0 +1,9 @@
+version: '1.0'
+services:
+  nginx:
+    build: .
+    ports:
+      # host : container
+      - "8081:80"
+    volumes:
+      - .:/usr/share/nginx/html

misc/how-to-contribute.html

@@ -123,9 +123,13 @@ <h3>Requirements:</h3>
 					</li>
 				</ul>
 				<h3>Optional</h3>
+				<span>A web server is required to load the page and all its components. <br> Docker setup: Open temrinal in the project's folder and type <span class="codeBlock">docker-compose up --build</span> to create a container running on port 8081</span>
 				<ul>
 					<li>
-						<a href="https://simplewebserver.org/" target="_blank" rel="noopener noreferrer">Local web-server</a> is needed to run the wiki on your machine, but not required to edit articles.
+						<a href="https://www.docker.com/" target="_blank" rel="noopener noreferrer">Docker</a>
+					</li>
+					<li>
+						<a href="https://simplewebserver.org/" target="_blank" rel="noopener noreferrer">Local web-server</a>
 					</li>
 				</ul>
 			</article>