Update index.md

Changed line 42

This change will help new users who follows this tutorial to get a working container as a result from building using the dockerfile commands proposed in lines 40-44, as expected to be.

See issue #121

docs/tutorial/our-application/index.md

@@ -39,7 +39,7 @@ see a few flaws in the Dockerfile below. But, don't worry! We'll go over them.
     ```dockerfile
     FROM node:12-alpine
     WORKDIR /app
-    COPY . .
+    COPY . /
     RUN yarn install --production
     CMD ["node", "src/index.js"]
     ```