Pre-existing fetchpriority won't be detected if there are spaces around the equal sign

[vmanthos]

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Describe the bug

We won't be adding the fetchpriority property if one already exists:

wp-rocket/inc/Engine/Media/AboveTheFold/Frontend/Controller.php

Line 135 in 134ac6a

if ( preg_match( '/fetchpriority=[\'"]([^\'"]+)[\'"]/', $matches[0] ) ) {

However, if it's added with spaces before of after the = sign like so:

<img src="https://example.com/dummy.png" fetchpriority = "high">

we will not detect it and add our own on top of it.

See the current RegEx in action: https://regex101.com/r/cqHgtE/1

To Reproduce
Steps to reproduce the behavior:

1. Add an LCP image to a page using the example code provided earlier.
2. After LCP has been processed by the SaaS, check the source code of the page.
3. Duplicate entries of the fetchpriority property will be there.

Expected behavior

The fetchpriority property should be correctly detected even if there are spaces before/after the = sign.

Screenshots

N/A

Additional context

N/A

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