chore(package): update xo to version 0.28.0

Closes #11

Author: greenkeeper[bot]

package.json

@@ -18,7 +18,7 @@
   "license": "MIT",
   "devDependencies": {
     "eslint-config-prettier": "^2.9.0",
-    "xo": "^0.20.2"
+    "xo": "^0.28.0"
   },
   "peerDependencies": {
     "micro": "^9.1.0"