fix: mount Svelte example and CLI template with Svelte 5 API

The svelte example and the native init Svelte scaffold both called
new App({ target }), the Svelte 4 component constructor. Svelte 5
removed it, so every checkout of examples/svelte and every freshly
generated Svelte project throws component_api_invalid_new on load.

Switch both to mount(App, { target }) from the svelte package.

Fixes #48

Author: mliem2k

changelog.d/svelte-mount-api.md

@@ -0,0 +1 @@
+fix: **Svelte example and template mount correctly on Svelte 5**: `main.js` used the removed Svelte 4 `new App({ target })` constructor, which throws `component_api_invalid_new` under Svelte 5. Both the `examples/svelte` app and the `native init` Svelte scaffold now mount with `mount(App, { target })` from `svelte`.

examples/svelte/frontend/src/main.js

@@ -1,6 +1,7 @@
+import { mount } from "svelte";
 import App from "./App.svelte";
 import "./app.css";
 
-const app = new App({ target: document.getElementById("app") });
+const app = mount(App, { target: document.getElementById("app") });
 
 export default app;

src/tooling/templates.zig

@@ -2589,10 +2589,11 @@ fn svelteIndexHtml(allocator: std.mem.Allocator, names: TemplateNames) ![]const
 
 fn svelteMainJs() []const u8 {
     return
+    \\import { mount } from "svelte";
     \\import App from "./App.svelte";
     \\import "./app.css";
     \\
-    \\const app = new App({ target: document.getElementById("app") });
+    \\const app = mount(App, { target: document.getElementById("app") });
     \\
     \\export default app;
     \\