chore(yaml): enforce .yaml extension and prefer double quotes in YAML via eslint-plugin-yml; fix rule name; format repo

prettier.config.mjs

@@ -16,7 +16,7 @@ export default {
       options: { proseWrap: 'preserve' },
     },
     {
-      files: ['*.yml', '*.yaml'],
+      files: ['*.yaml'],
       options: { singleQuote: false },
     },
     {