Explicitly add plugin-schema.json file because Typedoc does not appear to respect its inclusion from the tsconfig.json file.

packages/coreutils/package.json

@@ -26,7 +26,7 @@
   "scripts": {
     "build": "tsc -b",
     "clean": "rimraf lib",
-    "docs": "typedoc --options tdoptions.json --theme ../../typedoc-theme src",
+    "docs": "typedoc --options tdoptions.json --theme ../../typedoc-theme src src/plugin-schema.json",
     "prepublishOnly": "npm run build",
     "watch": "tsc -b --watch"
   },