Update plugins.md (#2197)

Author: Didier Franc

docs/docs/plugins.md

@@ -123,6 +123,7 @@ you can place the files in a `src` subfolder and build them to the plugin folder
 
 * [gatsby-plugin-antd](https://github.com/bskimball/gatsby-plugin-antd)
 * [gatsby-plugin-copy](https://github.com/aquilio/gatsby-plugin-copy)
+* [gatsby-plugin-google-fonts](https://github.com/didierfranc/gatsby-plugin-google-fonts)
 * [gatsby-plugin-i18n](https://github.com/angeloocana/gatsby-plugin-i18n)
 * [gatsby-plugin-i18n-tags](https://github.com/angeloocana/gatsby-plugin-i18n-tags)
 * [gatsby-plugin-i18n-readnext](https://github.com/angeloocana/gatsby-plugin-i18n-readnext)