Add build tools to fix arm64 build issue

Signed-off-by: Stefan Scherer <stefan.scherer@docker.com>

docs/tutorial/our-application/index.md

@@ -38,6 +38,7 @@ see a few flaws in the Dockerfile below. But, don't worry! We'll go over them.
 
     ```dockerfile
     FROM node:12-alpine
+    RUN apk add --no-cache python g++ make
     WORKDIR /app
     COPY . .
     RUN yarn install --production