Update dev-dependencies

Author: wooorm

package.json

@@ -48,7 +48,7 @@
     "remark-preset-wooorm": "^5.0.0",
     "remark-stringify": "^6.0.0",
     "tape": "^4.0.0",
-    "unified": "^7.0.0",
+    "unified": "^8.0.0",
     "unist-builder": "^1.0.0",
     "unist-util-remove-position": "^1.0.0",
     "xo": "^0.24.0"