Fixed outdated content

Signed-off-by: Kang HuaiShuai <khs1994@khs1994.com>

appendix/repo/nodejs.md

@@ -11,7 +11,7 @@
 在项目中创建一个 Dockerfile。
 
 ```bash
-FROM node:9
+FROM node:12
 # replace this with your application's default port
 EXPOSE 8888
 ```
@@ -31,7 +31,7 @@ $ docker run -it --rm \
     # -v "$(pwd)":/usr/src/myapp \
     --mount type=bind,src=`$(pwd)`,target=/usr/src/myapp \
     -w /usr/src/myapp \
-    node:9-alpine \
+    node:12-alpine \
     node your-daemon-or-script.js
 ```