Update CHANGELOG.md

Author: cristianoc

CHANGELOG.md

@@ -13,7 +13,7 @@
 # 12.0.0-alpha.12 (Unreleased)
 
 #### :bug: Bug fix
-- Fix issue wiht gentype and stdlib json. https://github.com/rescript-lang/rescript/pull/7378
+- Fix issue with gentype and stdlib json. https://github.com/rescript-lang/rescript/pull/7378
 
 # 12.0.0-alpha.11