Bump @babel/polyfill from 7.10.4 to 7.12.1

Bumps [@babel/polyfill](https://github.com/babel/babel/tree/HEAD/packages/babel-polyfill) from 7.10.4 to 7.12.1.
- [Release notes](https://github.com/babel/babel/releases)
- [Commits](https://github.com/babel/babel/commits/v7.12.1/packages/babel-polyfill)

---
updated-dependencies:
- dependency-name: "@babel/polyfill"
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

package.json

@@ -24,7 +24,7 @@
   "devDependencies": {
     "@babel/cli": "^7.8.4",
     "@babel/core": "^7.8.7",
-    "@babel/polyfill": "^7.8.7",
+    "@babel/polyfill": "^7.12.1",
     "@babel/preset-env": "^7.8.7",
     "cssnano": "^4.1.10",
     "glob": "^7.1.6",