chore: add initial Nu Validator error filters

.vnurc

@@ -0,0 +1,7 @@
+# Add regex filters for the Nu Validator error messages for proposed changes
+# not yet added to the validator.
+#
+# Proposed, tracking in gh-429
+Bad value “” for attribute “aria-activedescendant” on element “ul”:.*
+# Ignoring for Slider examples because it is forcing rule with role=img
+An “img” element must have an “alt” attribute, except under certain conditions. For details, consult guidance on providing text alternatives for images.

package.json

@@ -9,7 +9,7 @@
   "scripts": {
     "fix": "eslint --fix bin examples",
     "lint": "eslint bin examples",
-    "vnu-jar": "java -jar node_modules/vnu-jar/build/dist/vnu.jar --errors-only --no-langdetect examples/**/*.html",
+    "vnu-jar": "java -jar node_modules/vnu-jar/build/dist/vnu.jar --errors-only --filterfile .vnurc --no-langdetect examples/**/*.html",
     "test": "npm run lint && npm run vnu-jar"
   },
   "repository": {