docs(hooks): clarify mandatory 'type' field and update hook schema documentation (#17499)

docs/hooks/best-practices.md

@@ -91,6 +91,7 @@ spawning a process for irrelevant events.
   "hooks": [
     {
       "name": "validate-writes",
+      "type": "command",
       "command": "./validate.sh"
     }
   ]
@@ -584,6 +585,7 @@ defaults to 60 seconds, but you should set stricter limits for fast hooks.
         "hooks": [
           {
             "name": "fast-validator",
+            "type": "command",
             "command": "./hooks/validate.sh",
             "timeout": 5000 // 5 seconds
           }