feat(router): support optional catch all routes

[mhartington]

This allows for next-style optional catch-all routes.

PR Checklist

Closes # n/a

What is the new behavior?

For a more flexible routing setup, this allows for having a dynamic catch all routing setup, like nextjs provides.

For example, if you wanted to include a docs/ route, but did not want to hard-code every route that could be generated from it, you can use this new [[..slug]].page.ts syntax to support that.

.
└── app/
    ├── pages
    ├── docs/
    │   └── [[...slug]].page.ts  
    └── docs.page.ts

There's also an included example project for testing and validation that shows how this feature works in combination with markdown content.

Does this PR introduce a breaking change?

• Yes
• No

Other information

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[mhartington]

apologies for the delay here @brandonroberts. we're looking good in testing!

[brandonroberts]

No worries, nice work!

[SOG-web]

This came in right on time

Thanks @mhartington @brandonroberts