Add ability to pass in vite / astro configurations for doc core

[dlabaj]

Doc core uses Vite and Astro configuration under the hood. While wrapping Astros functionality hides a lot of the nuances of using these frameworks and packages it does present an issue when needing to build, deploy, and update configurations for products using the doc core. Changes currently need to made directly doc core and a new release needs to be delivered to npm. This is an issue if you would like to deploy say AWS , CloudFlare, or Surge. In order to do this packages for deploying to these services need to be updated in patternfly doc core, and each of these services require drastically different packages and configurations for Astro.

To solve this we need the ability to do the following:"

• Allow consumers to modify or extend functionality in astro.config.mjs. This includes items we currently do not account for in the CLI. We have no way of knowing what a user may need to update in this file so we should not limit them to only items that are set via the cli.
• Add ability to add additional packages that can be installed in the consumers node modules folder and used by the doc core framework. This will allow users to configure their CI/CD environments to suit how they build and where they will deliver their content too.