fix(gatsby): PageProps TS type: add params (#26974)

* PageProps type: add `params`

URL parameters when the page has a `matchPath`

* `params` is actually always present

Co-authored-by: gatsbybot <[email protected]>

Author: antoinerousseau

packages/gatsby/index.d.ts

@@ -78,6 +78,8 @@ export type PageProps<
   children: undefined
   /** @deprecated use pageContext instead */
   pathContext: object
+  /** The URL parameters when the page has a `matchPath` */
+  params: Record<string, string>
   /** Holds information about the build process for this component */
   pageResources: {
     component: React.Component