[bug] web_dev_server removes HTML template element contents

[AlainSchneble]

Describe the bug

When serving html files through web_dev_server by using cargo tauri dev, any template element contents in the served HTML are removed.

While looking further into this issue, the culprit seem to be this:

tauri/tooling/cli/src/helpers/web_dev_server.rs

Line 129 in db7765e

f = document.to_string().as_bytes().to_vec();

FMPOV, this should be changed to:

f = tauri_utils::html::serialize_node(&document);

(I've actually tried this change out and it solves the issue)

A similar issue has already been fixed for the assets compilation process / asset csp modification, see #5247 (and also #4410) but the web_dev_server hasn't catched up with this change.

Reproduction

1. cargo create-tauri-app

2. Select plain vanilla HTML/CSS/JavaScript

3. Add the following template element before the closing body tag in src/index.html:

<template>
    <tr>
        <td>[ID]</td>
        <td>[Name]</td>
    <tr>
</template>

4. cargo tauri dev
5. Inspect the DOM and observe that the template element is empty

Expected behavior

HTML template element contents should be served properly.

For the example above, I would expect to see the following children when inspecting the DOM:

<template>
    #document-fragment
        <tr>
            <td>[ID]</td>
            <td>[Name]</td>
        <tr>
</template>

Platform and versions

Environment
  › OS: Windows 10.0.19045 X64
  › Webview2: 109.0.1518.69
  › MSVC:
      - Visual Studio Community 2022
      - Visual Studio Community 2019
  › Node.js: 19.1.0
  › npm: 8.19.3
  › pnpm: Not installed!
  › yarn: Not installed!
  › rustup: 1.25.1
  › rustc: 1.66.1
  › cargo: 1.66.1
  › Rust toolchain: stable-x86_64-pc-windows-msvc 

Packages                                       
WARNING: no lock files found, defaulting to npm
  › @tauri-apps/cli [NPM]: 1.2.3
  › @tauri-apps/api [NPM]: Not installed!
  › tauri [RUST]: 1.2.4,
  › tauri-build [RUST]: 1.2.1,
  › tao [RUST]: 0.15.8,
  › wry [RUST]: 0.23.4,

App
  › build-type: bundle
  › CSP: default-src 'self'
  › distDir: ../src
  › devPath: ../src
package.json not found

App directory structure
  ├─ .vscode
  ├─ src
  └─ src-tauri

Stack trace

No response

Additional context

No response