build(deps): update dependency workbox-cli to v6 (#70)

Co-authored-by: Renovate Bot <[email protected]>

Author: renovate[bot]

package.json

@@ -2,7 +2,7 @@
   "name": "docs",
   "devDependencies": {
     "prettier": "2.0.5",
-    "workbox-cli": "5.1.3"
+    "workbox-cli": "6.1.2"
   },
   "scripts": {
     "style": "prettier --check .",