Fix svelte story files not reloading (#362)

Fixes #52

Svelte story files have the same issue as react story files.  The webpack HMR seems to prevent vite's HMR from working correctly, so we need to exclude story files as HMR boundaries in vite.  The svelte plugin doesn't expose as nice of a way to do this, but thanks to a suggestion from @domyen in sveltejs/vite-plugin-svelte#321 (comment), I was able to make it work.

To test:
Start up the svelte example, edit a `.stories.svelte` file, and confirm that the page reloads and shows your changes.

packages/builder-vite/vite-config.ts

@@ -52,7 +52,7 @@ export async function commonConfig(
 
 export async function pluginConfig(options: ExtendedOptions, _type: PluginConfigType) {
   const { framework, presets } = options;
-  const svelteOptions = await presets.apply('svelteOptions', {}, options);
+  const svelteOptions: Record<string, any> = await presets.apply('svelteOptions', {}, options);
 
   const plugins = [
     codeGeneratorPlugin(options),
@@ -82,7 +82,27 @@ export async function pluginConfig(options: ExtendedOptions, _type: PluginConfig
   if (framework === 'svelte') {
     try {
       const sveltePlugin = require('@sveltejs/vite-plugin-svelte').svelte;
-      plugins.push(sveltePlugin(svelteOptions));
+
+      // We need to create two separate svelte plugins, one for stories, and one for other svelte files
+      // because stories.svelte files cannot be hot-module-reloaded.
+      // Suggested in: https://github.com/sveltejs/vite-plugin-svelte/issues/321#issuecomment-1113205509
+
+      // First, create an array containing user exclude patterns, to combine with ours.
+      const userExclude = Array.isArray(svelteOptions?.exclude)
+        ? svelteOptions?.exclude
+        : svelteOptions?.exclude
+        ? [svelteOptions?.exclude]
+        : [];
+
+      // These are the svelte stories we need to exclude from HMR
+      const storyPatterns = ['**/*.story.svelte', '**/*.stories.svelte'];
+      // Non-story svelte files
+      plugins.push(sveltePlugin({ ...svelteOptions, exclude: [...userExclude, ...storyPatterns] }));
+      // Svelte stories without HMR
+      plugins.push({
+        ...sveltePlugin({ ...svelteOptions, exclude: userExclude, include: storyPatterns, hot: false }),
+        name: 'vite-plugin-svelte-stories',
+      });
     } catch (err) {
       if ((err as NodeJS.ErrnoException).code !== 'MODULE_NOT_FOUND') {
         throw new Error(