fix: add typescript support in .svelte files

.changes/fix-typescript-in-svelte-and-sveltekit.md

@@ -0,0 +1,7 @@
+---
+"create-tauri-app": patch
+---
+
+Fixed an [issue](https://github.com/tauri-apps/create-tauri-app/issues/276) where typescript was not working inside .svelte files in the svelte-kit-ts and svelte-ts templates. In both cases, this was due to the lack of a preprocessor. This was fixed differently in each template.
+
+For sveltekit, the preprocessor was added to the svelte.config.js file. For svelte, the preprocessor was added to the vite.config.js file. For svelte, this required adding svelte-preprocess as a dev dependency.

packages/cli/fragments/fragment-svelte-kit-ts/svelte.config.js

@@ -1,7 +1,9 @@
 import staticAdapter from "@sveltejs/adapter-static";
+import { vitePreprocess } from "@sveltejs/kit/vite";
 
 /** @type {import('@sveltejs/kit').Config} */
 const config = {
+  preprocess: [vitePreprocess()],
   kit: {
     adapter: staticAdapter(),
   },

packages/cli/fragments/fragment-svelte-ts/package.json

@@ -19,6 +19,7 @@
     "@tsconfig/svelte": "^3.0.0",
     "svelte": "^3.54.0",
     "svelte-check": "^2.10.0",
+    "svelte-preprocess": "^5.0.0",
     "tslib": "^2.4.1",
     "typescript": "^4.6.4",
     "vite": "^4.0.0",

packages/cli/fragments/fragment-svelte-ts/vite.config.ts

@@ -1,9 +1,10 @@
 import { defineConfig } from "vite";
 import { svelte } from "@sveltejs/vite-plugin-svelte";
+import sveltePreprocess from "svelte-preprocess";
 
 // https://vitejs.dev/config/
 export default defineConfig({
-  plugins: [svelte()],
+  plugins: [svelte({ preprocess: [sveltePreprocess({ typescript: true })] })],
 
   // Vite options tailored for Tauri development and only applied in `tauri dev` or `tauri build`
   // prevent vite from obscuring rust errors