fix(cli): web_dev_server html template serialization (fix #6165)

[AlainSchneble]

What kind of change does this PR introduce?

• Bugfix
• Feature
• Docs
• New Binding issue #___
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change?

• Yes, and the changes were approved in issue #___
• No

I believe this change is safe because this serialization is already used in https://github.com/tauri-apps/tauri/pull/5247/files#diff-45b0f313a4e403c382fbd52d97cb3cc15d75f09a30a9cca633c4c6d29a24590eR83 (note that there, the function has been aliased, but it is actually the same) and hence is already used when compiling assets.

Checklist

• When resolving issues, they are referenced in the PR's title (e.g fix: remove a typo, closes #___, #___)
• A change file is added if any packages will require a version bump due to this PR per the instructions in the readme.
• I have added a convincing reason for adding this feature, if necessary

Other information

Related issue, see #6165

Also note that according to html5ever issue servo/html5ever#464, html (template) serialization has to be handled by the crate that uses html5ever, i.e. tauri so to speak.

[lucasfernog]

We got the existing fix from kuchiki-rs/kuchiki#96, thanks for this PR!