Adds `rel` parameter to the social icons configuration documentation (#987)

Alexander Lazarević

2 days ago eea6dfd3fe4b97518d2c5d2fb550e906793507e8

 CONTRIBUTORS.md

@@ -148,3 +148,4 @@
-   [Matt Ellery](https://github.com/matt-ellery)
-   [Daniel Olshansky](https://github.com/olshansk)
-   [Gregor Podjed](https://github.com/gragorther)
-   [Alexander Lazarević](https://e11bits.com)