(fix) align type def with Svelte type def

props are optional (for some to me unknown reason, it's wrong), but to align it with SvelteComponentDev and to avoid type errors, we need to make it optional here, too.

Author: dummdidumm

packages/svelte2tsx/svelte-shims.d.ts

@@ -39,7 +39,7 @@ declare class Svelte2TsxComponent<
      * `component.$set({ x: 1 })` is equivalent to `x = 1` inside the component's `<script>` block.
      * Calling this method schedules an update for the next microtask — the DOM is __not__ updated synchronously.
      */
-    $set(props: Partial<Props>): void;
+    $set(props?: Partial<Props>): void;
     // From SvelteComponent(Dev) definition
     $$: any;
     $capture_state(): void;