LCP preload won't be added to a page if there is a space in the closing title tag

[vmanthos]

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Describe the bug

We rely on detecting </title> to add preloaded LCP on a page:
https://github.com/wp-media/wp-rocket/blob/9e73f9473c9c5a3d194ad87564eafe43438d3fea/inc/Engine/Media/AboveTheFold/Frontend/Controller.php

If instead of </title> the theme adds </title >, which is still valid, we won't add the code to preload the LCP to the page.

That kind of scenario would be possible for themes that don't use add_theme_support( 'title-tag' ); and are adding the <title></title> on their own, or for specific templates.

To Reproduce
Steps to reproduce the behavior:

1. Use the following template to create a page: https://github.com/wp-media/rocket-test-data/blob/master/templates/title_tag_with_space.php
2. After LCP has been processed by the SaaS check the source code of the page.
3. The LCP image will not be preloaded.

Expected behavior

We should be able to correctly append the preloaded LCP to </title >.

Additional context

N/A

Acceptance Criteria (for WP Media team use only)
Clear instructions for developers, to be added before the grooming