fix: Drop npm from package.json engines config (fixes #476)

Author: eemeli

docs/CONTRIBUTING.md

@@ -31,7 +31,7 @@ To start hacking `yaml`, this should get you set up:
 git clone https://github.com/eemeli/yaml.git # or your own fork
 cd yaml
 git submodule update --init # required by tests; also fetches the docs & playground
-npm install
+npm install # npm v7 or later is required
 npm test # just to be sure
 ```
 

package-lock.json

@@ -90,7 +90,6 @@
     "typescript": "^5.0.3"
   },
   "engines": {
-    "node": ">= 14",
-    "npm": ">= 7"
+    "node": ">= 14"
   }
 }