Update xo

Reviewed-by: Christian Murphy <christian.murphy.42@gmail.com>
Reviewed-by: Remco Haszing <remcohaszing@gmail.com>
Reviewed-by: Titus Wormer <tituswormer@gmail.com>

Closes GH-20.

Author: cowboyd

package.json

@@ -78,7 +78,7 @@
     "type-coverage": "^2.0.0",
     "typescript": "^4.0.0",
     "unist-builder": "^3.0.0",
-    "xo": "^0.53.0"
+    "xo": "^0.54.0"
   },
   "scripts": {
     "prepack": "npm run build && npm run format",