Update babel monorepo to v7.12.0

Author: renovate-bot

package.json

@@ -32,11 +32,11 @@
     "@aureooms/js-pairing-heap": "^1.0.0"
   },
   "devDependencies": {
-    "@babel/cli": "7.11.6",
-    "@babel/core": "7.11.6",
+    "@babel/cli": "7.12.0",
+    "@babel/core": "7.12.0",
     "@babel/polyfill": "7.11.5",
-    "@babel/preset-env": "7.11.5",
-    "@babel/register": "7.11.5",
+    "@babel/preset-env": "7.12.0",
+    "@babel/register": "7.12.0",
     "ava": "3.13.0",
     "coveralls": "3.1.0",
     "esdoc": "1.1.0",