Update CHANGELOG.md

Author: daattali

CHANGELOG.md

@@ -18,6 +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 link for Discord (#907)
 
 ## v5.0.0 (2020-09-15)