Fix typo: verison -> version (#663)

Co-authored-by: Fabrizio Ferrai <[email protected]>

Author: JordanMartinez

README.md

@@ -480,7 +480,7 @@ In this case, we can just change the override to point to some commit of our for
 let upstream = -- <package set URL here>
 in  upstream
   with simple-json.repo = "https://github.com/my-user/purescript-simple-json.git"
-  with simple-json.verison = "701f3e44aafb1a6459281714858fadf2c4c2a977"
+  with simple-json.version = "701f3e44aafb1a6459281714858fadf2c4c2a977"
 ```
 
 **Note**: you can use a "branch", a "tag" or a "commit hash" as a `version`.