fix: improve indent of built html file

[gnehcwu]

Description

Improve the indent in final built html file.

Additional context

Not sure if it is too picky or not, when build a project, injecting processed links/scripts into head with proper indent looks slightly better.

Before:

After:

---

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Before submitting the PR, please make sure you do the following

• Read the Contributing Guidelines.
• Read the Pull Request Guidelines and follow the Commit Convention.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Ideally, include relevant tests that fail without this PR but pass with it.

[Shinigami92]

Could you show a screenshot of the html code, preferably a before vs after? 🙂

[gnehcwu]

Updated the PR description with screenshots for a comparison, please kindly check @Shinigami92