fix(package): update github-slugger to version 1.1.3

Author: greenkeeper[bot]

package.json

@@ -27,7 +27,7 @@
     "get-comments": "^1.0.1",
     "get-port": "^3.1.0",
     "git-url-parse": "^6.0.1",
-    "github-slugger": "1.1.1",
+    "github-slugger": "1.1.3",
     "glob": "^7.0.0",
     "globals-docs": "^2.3.0",
     "highlight.js": "^9.1.0",