🤖 chore: Add cover key in .babel.env.

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  - https://github.com/aureooms/rejuvenate/blob/b7b7316fcc320ee7d249b0aa391d9a196c944421/src/transforms/package.json:ensure-babel-env-cover.js
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Author: a-flying-potato

package.json

@@ -94,7 +94,8 @@
     "env": {
       "development": {
         "sourceMaps": "inline"
-      }
+      },
+      "cover": {}
     }
   },
   "xo": {