Allow extra parameters when generating static pages

[tomhicks]

Feature request

Is your feature request related to a problem? Please describe.

I have an API that is cursor paginated, but I would like to create a page-number based index page. Because getStaticProps only receives the page route params, I cannot achieve these nice URLs.

Describe the solution you'd like

Let me return a superset of the required params from getStaticPaths, then I can use those in getStaticProps.

e.g. route is /articles/page/[page]

Let me return the following from getStaticPaths:
[{page: 1, cursor: undefined}, {page: 2, cursor: 'abc123'}]

so in getStaticProps I can do:

const articles = await api.getAritclePage(limit: 12, startAfter: ctx.cursor)

Describe alternatives you've considered

Alternatives would be:
• redo all the pagination work again in gsProps which is wasteful
• have URLs like /articles/cursor/[cursor] which isn't as nice

Additional context

None