ci(docs): Use eslint plugin for automatic JSX runtime

Ref: https://docusaurus.io/docs/migration/v3#automatic-jsx-runtime
and https://github.com/jsx-eslint/eslint-plugin-react/blob/master/docs/rules/react-in-jsx-scope.md#when-not-to-use-it

docs/.eslintrc.js

@@ -8,6 +8,7 @@ module.exports = {
   extends: [
     "eslint:recommended",
     "plugin:react/recommended",
+    "plugin:react/jsx-runtime",
     "plugin:mdx/recommended",
     "prettier",
   ],