Filter to exclude elements from LCP

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Describe the bug In some edge cases, discovered LCP will be inaccurate and getting the proper element will require extensive logic and comparison, or will just not be possible.

We need a filter to help exclude LCP element depending on their selector or image path fragment.

The following worked on a website with the issue:

Replacing:

const firstElementWithInfo = elements.find(item => item.elementInfo !== null);

Under _initWithFirstElementWithInfo(elements) { ... } with:

const selectorsToExclude = ['.selector'];
const imagesToExclude = ['frament/path/to/image.jpg'];

const firstElementWithInfo = elements.find(item => 
  item.elementInfo !== null && 
  !selectorsToExclude.some(selector => item.element.matches(selector)) &&
  !imagesToExclude.some(image => 
    (item.elementInfo.src && item.elementInfo.src.includes(image)) || 
    (item.elementInfo.srcset && item.elementInfo.srcset.includes(image))
  )
);

To Reproduce For testing, you can simulate it using:

https://woodmart.xtemos.com/blog/category/wooden-accessories/?opt=blog_default

By adding the following style to simulate the issue:

.main-page-wrapper {
    background-image: url(https://images.pexels.com/photos/214574/pexels-photo-214574.jpeg?auto=compress&cs=tinysrgb&w=50&dpr=1);
    background-repeat: no-repeat;
}

and test excluding either:

const selectorsToExclude = ['.main-page-wrapper'];
const imagesToExclude = ['214574/pexels-photo-214574.jpeg'];

Expected behavior Customers, support, product (for known layouts), should be able to exclude inaccurate LCP element when needed.

Screenshots N/A

Additional context Slack discussion - https://wp-media.slack.com/archives/C08N8J6VC/p1719941962200769?thread_ts=1719857870.817579&cid=C08N8J6VC

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

wp-media / wp-rocket

Filter to exclude elements from LCP #6757