Navigation Link: Add Border and Spacing support

[karthick-murugan]

What?

Add border and spacing block support to the Navigation Link( Custom Link ) block.

Part of #43247
Part of #43243

Why?

Navigation Link( Custom Link ) block is missing border and spacing support.

How?

Adds the border and spacing block support in block.json

Testing Instructions

• Go to Appearance > Editor > Styles > Edit Styles > Blocks.
• Ensure the Navigation Link( Custom Link ) block’s border and spacing are configurable via Global Styles.
• Confirm Global Styles apply correctly in both the Editor and Frontend.
• Open the Page or Template where you want to add the menu.
• Add a Navigation block (the container block for all navigation links).
• If WordPress detects pre-existing menus, it may prompt you to start with an existing menu. Choose Create a new menu if starting fresh.
• Within the Navigation block, select any pre-existing page links.
• That is the Navigation Link( Custom Link ) block and the block name could be a Custom Link, Post Link, Page Link, Category Link, or Tag Link, depending on its type.
• Verify Border, Radius, and Spacing settings are available for this link.
• Check that block-specific styles (e.g., borders, spacing) take precedence over Global Styles.
• Ensure borders and spacing display correctly in both the Editor and Frontend.

Testing Instructions for Keyboard

Screenshots or screencast

In Backend:

In Frontend:

[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

If you're merging code through a pull request on GitHub, copy and paste the following into the bottom of the merge commit message.

Co-authored-by: karthick-murugan <karthickmurugan@git.wordpress.org>

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.

[github-actions]

👋 Thanks for your first Pull Request and for helping build the future of Gutenberg and WordPress, @karthick-murugan! In case you missed it, we'd love to have you join us in our Slack community.

If you want to learn more about WordPress development in general, check out the Core Handbook full of helpful information.

[karthick-murugan]

@t-hamano - Please have a look at this PR, when you get some time.