Add prettier to docs/ (#4628)

docs/.prettierrc.js

@@ -0,0 +1,16 @@
+import { readFile } from 'node:fs/promises';
+
+// eslint-disable-next-line antfu/no-top-level-await
+const config = JSON.parse(await readFile(new URL('../.prettierrc.json', import.meta.url)));
+
+export default {
+  ...config,
+  plugins: ['@ianvs/prettier-plugin-sort-imports'],
+  importOrder: [
+    '<THIRD_PARTY_MODULES>', // Imports not matched by other special words or groups.
+    '', // Empty string will match any import not matched by other special words or groups.
+    '^(#|@|~|\\$)(/.*)$',
+    '',
+    '^[./]',
+  ],
+};