chore(package): update xo to version 0.28.0

Closes #7

Author: greenkeeper[bot]

package.json

@@ -20,7 +20,7 @@
   },
   "devDependencies": {
     "eslint-config-prettier": "^2.0.0",
-    "xo": "^0.20.2"
+    "xo": "^0.28.0"
   },
   "peerDependencies": {
     "micro": "^9.1.0"