Update dependency yargs to v15 (#27)

Author: renovate[bot]

package.json

@@ -32,7 +32,7 @@
     "js-yaml": "^3.13.1",
     "json5": "^2.1.0",
     "vue-template-compiler": "^2.6.10",
-    "yargs": "^13.3.0"
+    "yargs": "^15.0.0"
   },
   "devDependencies": {
     "@types/debug": "^4.1.4",