Update dependency xo to v0.26.1

Author: renovate-bot

package.json

@@ -12,7 +12,7 @@
     "markdownlint-cli": "0.13.0",
     "prettier": "1.11.1",
     "prettier-check": "2.0.0",
-    "xo": "0.20.3"
+    "xo": "0.26.1"
   },
   "scripts": {
     "ci": "rm -fr node_modules && yarn install --frozen-lockfile",