feat: add sveltekit html parser

- add sveltekit html parser
- add npm package
- add README.md

Author: ntsd

.gitignore

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+/node_modules/

README.md

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+# Sveltekit HTML Minifier
+
+Sveltekit Adapter to Minify the preload HTML page in case using CSR/Preload by [html-minifier-terser](https://github.com/terser/html-minifier-terser).
+
+## Installation
+
+`npm i -D sveltekit-html-minifier`
+
+## Usage
+
+Add the adapter to your `svelte.config.js` file. Place your default adapter as the first parameter. This will run after the default adapter has finished rendering.
+
+```js
+import adapter from "@sveltejs/adapter-static";
+import htmlMinifierAdaptor from "sveltekit-html-minifier";
+
+export default {
+  kit: {
+    adapter: htmlMinifierAdaptor(adapter()),
+  },
+};
+```
+
+### Options
+
+You can pass additional options to the adapter. For example
+
+```js
+import adapter from "@sveltejs/adapter-static";
+import htmlMinifierAdaptor from "sveltekit-html-minifier";
+
+export default {
+  kit: {
+    adapter: htmlMinifierAdaptor(
+      adapter({
+        pages: "build",
+      }),
+      {
+        // your build path (same as adapter static pages)
+        pages: "build",
+        // custom html-minifier-terser options
+        // https://github.com/terser/html-minifier-terser#options-quick-reference
+        minifierOptions: {},
+      }
+    ),
+  },
+};
+```
+
+- `pages` (string): Specifies the build path. This should be the same as the adapter static pages.
+- `minifierOptions` (object): Custom options for [html-minifier-terser](https://github.com/terser/html-minifier-terser#options-quick-reference).

index.d.ts

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+import { Adapter } from "@sveltejs/kit";
+import { type Options as minifierOptions } from "html-minifier-terser";
+
+interface Options {
+  pages?: string;
+  minifierOptions?: minifierOptions;
+}
+
+export default function adapter(
+  insideAdapter?: Adapter,
+  options?: Options
+): Adapter;

index.js

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+import path from "node:path";
+import { readFileSync, writeFileSync } from "node:fs";
+import minifier from "html-minifier-terser";
+
+/** @type {import('.').default} */
+export default function (insideAdapter, options) {
+  const name = "sveltekit-html-minifier";
+  return {
+    name: insideAdapter ? `${name}, ${insideAdapter.name}` : name,
+    async adapt(builder) {
+      if (insideAdapter) {
+        await insideAdapter.adapt(builder);
+      }
+
+      /** @type {import('.').Options} */
+      const mergedOptions = {
+        pages: "build",
+        ...options,
+        minifierOptions: {
+          removeAttributeQuotes: true,
+          minifyJS: true,
+          minifyCSS: true,
+          collapseWhitespace: true,
+          useShortDoctype: true,
+          ...options?.minifierOptions,
+        },
+      };
+
+      builder.prerendered.pages.forEach(async (page) => {
+        const htmlPath = path.join(mergedOptions.pages, page.file);
+
+        builder.log.info(`Minify HTML ${htmlPath}`);
+
+        // read HTML file
+        const html = readFileSync(htmlPath).toString();
+
+        // minify HTML
+        const minHTML = await minifier.minify(
+          html,
+          mergedOptions.minifierOptions
+        );
+
+        // write minified HTML
+        await writeFileSync(htmlPath, minHTML);
+      });
+    },
+  };
+}