Update dev-dependencies

Author: wooorm

package.json

@@ -24,7 +24,7 @@
   },
   "devDependencies": {
     "browserify": "^16.0.0",
-    "deepmerge": "^2.0.0",
+    "deepmerge": "^3.0.0",
     "hast-util-to-html": "^5.0.0",
     "hastscript": "^5.0.0",
     "nyc": "^13.0.0",