link prefetch new feature

[geckod22]

Proposed changes

The changes are to add a new feature to the module called Link Prefetch. This make the admin able to set if and how the links should be prefetched to provide a faster navigation among the pages.
https://jira.newfold.com/browse/PRESS7-64

Type of Change

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)

Video

Checklist

• I have read the CONTRIBUTING doc
• I have viewed my change in a web-browser
• Linting and tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

Further comments

Depending on the selected options, the frontend js will manage the behaviour of this feature as explained in the options description texts. It will add a link rel=prefetch tag in the page header.

On Desktop:

1. Prefetch on Mouse Hover (Recommended): the js will add the link tag after 60ms of the mouse hover so the broswer will prefetch and the link and when the actual redirection happen the loading will be faster.
2. Prefetch on Mouse down: normally the click on a link really happens when the mouse button is released, and not when the button is pressed as one could imagine. So with this option we start to prefetch the link as soon as the mouse button is pressed.

On Mobile:

1. Prefetch on Touchstart (Recommended): it is like the Mouse down option for desktop.
2. Prefetch Above the Fold: in this case the js will prefetch all the links in the current view

[chrisdavidmiles]

Awaiting code review from @arunshenoy99

[arunshenoy99]

Hey @geckod22, thank you for the PR! Great work, especially since this is your first time working on this codebase. I’ve added a few minor comments and suggestions for optimisations. Please check and let me know if they make sense.

Also:

• Let’s make sure to run the wp-scripts linter on the JS files.
• Let’s add a newline at the end of each file to maintain consistency.

[arunshenoy99]

Looks good to me. Thanks a lot @geckod22