Add Empty String As Undefined to ct3env File

[Lermatroid]

Like the following to mark empty strings as undefined instead of having to add ".min(1)"

  /**
   * Makes it so that empty strings are treated as undefined. `SOME_VAR: z.string()` and
   * `SOME_VAR=''` will throw an error.
   */
  emptyStringAsUndefined: true

[linear]

HK-139 Add Empty String As Undefined to ct3env File