Update Prerequisites nodejs version (#4538)

* Update Prerequisites nodejs version

* Update how-to-contribute.md

Author: Noel Kim (김민혁)

content/docs/how-to-contribute.md

@@ -103,7 +103,7 @@ In order to accept your pull request, we need you to submit a CLA. You only need
 
 ### Contribution Prerequisites {#contribution-prerequisites}
 
-* You have [Node](https://nodejs.org) installed at v8.0.0+ and [Yarn](https://yarnpkg.com/en/) at v1.2.0+.
+* You have [Node](https://nodejs.org) installed at LTS and [Yarn](https://yarnpkg.com/en/) at v1.2.0+.
 * You have [JDK](https://www.oracle.com/technetwork/java/javase/downloads/index.html) installed.
 * You have `gcc` installed or are comfortable installing a compiler if needed. Some of our dependencies may require a compilation step. On OS X, the Xcode Command Line Tools will cover this. On Ubuntu, `apt-get install build-essential` will install the required packages. Similar commands should work on other Linux distros. Windows will require some additional steps, see the [`node-gyp` installation instructions](https://github.com/nodejs/node-gyp#installation) for details.
 * You are familiar with Git.