Update readme for node version

Author: majunze2001

README.md

@@ -12,6 +12,8 @@ node_modules/.bin/hexo new news "News Title"
 ```
 
 ## Testing Locally
+Use Node.js 16, because there are known issues with newer versions. [nvm](https://github.com/nvm-sh/nvm) is recommended.
+
 You can start a server locally.
 ```
 npm start