Create initial vip-config.php file

### Description

The configure script creates the `vip-config` folder, but not the `vip-config.php` file that belongs in it.

### Use Case

When creating a project based off of this repo and selecting WordPress VIP as the target, the baseline `vip-config.php` file should be copied from VIP's skeleton.

### Acceptance Criteria
- When running the configure script and specifying VIP as the target, copy the [VIP Go Skeleton vip-config.php file](https://github.com/Automattic/vip-go-skeleton/blob/production/vip-config/vip-config.php) into the newly created `vip-config` folder.