chore(package): update xo to version 0.28.0

Author: greenkeeper[bot]

package.json

@@ -27,7 +27,7 @@
     "p-retry": "^4.0.0",
     "semantic-release": "^17.0.0",
     "tempy": "^0.5.0",
-    "xo": "^0.27.0"
+    "xo": "^0.28.0"
   },
   "homepage": "https://github.com/semantic-release/npm-registry-docker#readme",
   "keywords": [
@@ -78,6 +78,9 @@
   },
   "xo": {
     "prettier": true,
-    "space": true
+    "space": true,
+    "rules": {
+      "unicorn/string-content": "off"
+    }
   }
 }