docs: rename "prepublish" to "prepublishOnly" (#826)

Update the v5 documentation to be in line with pinst [1] by replacing the (deprecated) "prepublish" hook with "prepublishOnly".

--
1. https://github.com/typicode/pinst

docs/README.md

@@ -58,7 +58,7 @@ yarn husky install
   "private": false,
   "scripts": {
     "postinstall": "husky install",
-    "prepublish": "pinst --disable",
+    "prepublishOnly": "pinst --disable",
     "postpublish": "pinst --enable"
   }
 }