Bump @babel/core from 7.15.5 to 7.15.8 in /assets (#294)

Author: dependabot[bot]

assets/package-lock.json

@@ -18,7 +18,7 @@
     "phoenix_live_view": "file:../deps/phoenix_live_view"
   },
   "devDependencies": {
-    "@babel/core": "^7.15.5",
+    "@babel/core": "^7.15.8",
     "@babel/preset-env": "^7.15.8",
     "babel-eslint": "^10.1.0",
     "babel-loader": "^8.2.1",