blog:

en-us:

1. gsoc-2018.md | Add SEO of header in mankdown
2. dubbo2-js.md | Fix typo - 'keywords' of SEO in mankdown (跨语言）
3. prepare-an-apache-release.md | Add 'description' content in SEO header; and add the title('#') in the article.

zh-cn:

1. prepare-an-apache-release.md | Add 'description' content in SEO header.
2. dubbo-contribute-to-opensource.md | 'contribue' --> 'contribute'