Add js web stuff to landing page + documentation

go/jsruntime/runtime/@solidjs/router/dist/lifecycle.d.ts

@@ -0,0 +1,5 @@
+import { BeforeLeaveLifecycle, LocationChange } from "./types.js";
+export declare function createBeforeLeave(): BeforeLeaveLifecycle;
+export declare function saveCurrentDepth(): void;
+export declare function keepDepth(state: any): any;
+export declare function notifyIfNotBlocked(notify: (value?: string | LocationChange) => void, block: (delta: number | null) => boolean): () => void;