docs(router): fix docs related to parsed state (#3194)

* docs(router): fix docs related to parsed state

* docs(router): clarify usage of history state interface

* ci: apply automated fixes

* mention file where history state should be extended

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

docs/framework/react/api/router.md

@@ -60,6 +60,7 @@ title: Router API
   - [`MatchRouteOptions Type`](./router/MatchRouteOptionsType.md)
   - [`NavigateOptions Type`](./router/NavigateOptionsType.md)
   - [`NotFoundError Type`](./router/NotFoundErrorType.md)
+  - [`ParsedHistoryState Type`](./router/ParsedHistoryStateType.md)
   - [`ParsedLocation Type`](./router/ParsedLocationType.md)
   - [`Redirect Type`](./router/RedirectType.md)
   - [`Register Type`](./router/RegisterType.md)

docs/framework/react/api/router/ParsedHistoryStateType.md

@@ -0,0 +1,13 @@
+---
+id: ParsedHistoryStateType
+title: ParsedHistoryState type
+---
+
+The `ParsedHistoryState` type represents a parsed state object. Additionally to `HistoryState`, it contains the index and the unique key of the route.
+
+```tsx
+export type ParsedHistoryState = HistoryState & {
+  key?: string
+  __TSR_index: number
+}
+```

docs/framework/react/api/router/ParsedLocationType.md

@@ -11,7 +11,7 @@ interface ParsedLocation {
   pathname: string
   search: TFullSearchSchema
   searchStr: string
-  state: HistoryState
+  state: ParsedHistoryState
   hash: string
   maskedLocation?: ParsedLocation
   unmaskOnReload?: boolean

docs/framework/react/api/router/historyStateInterface.md

@@ -8,7 +8,13 @@ The `HistoryState` interface is an interface exported by the `history` package t
 You can extend this interface to add additional properties to the state object across your application.
 
 ```tsx
-interface HistoryState {
-  key: string // This is the unique ID for any given history entry
+// src/main.tsx
+declare module '@tanstack/react-router' {
+  // ...
+
+  interface HistoryState {
+    additionalRequiredProperty: number
+    additionalProperty?: string
+  }
 }
 ```