add news item for hacerrank

Author: daattali

CHANGELOG.md

@@ -18,7 +18,7 @@
 - Fixed bug where staticman didn't work jQuery slim version is used (#766)
 - Fixed very long strings to wrap around the next line rather than go off-screen (#787)
 - Added `footer-hover-col` config setting to customize the hover colour of links in the footer (#848)
-- Added social network links for Discord (#907) and Kaggle (#961)
+- Added social network links for Discord (#907), Kaggle (#961), and Hackerrank (#978)
 
 ## v5.0.0 (2020-09-15)