Fix for navigation anchor links to close modal

[coreyworrell]

What?

Allows the navigation block modal to close if you click on an item that is linked to an anchor on the current page.

Why?

Currently links like /#anchor or /some-page/#anchor do not close the modal. It only closes if the href exactly starts with #. So if you are on /some-page/ and you click the /some-page/#anchor link, it will scroll down to the anchor, but the modal will remain open.

How?

Modified the link click handler to test if the href contains a hash and it matches the current page (protocol, host, pathname, and search).

Testing Instructions

1. Insert a Navigation block (in header through Site Editor for example), make sure modal is set to mobile or always.
2. Insert a navigation item to a page such as /page/#anchor
3. From other page (not /page/), open modal menu, click link. Modal should remain open as browser navigation happens.
4. From new page /page/, open modal menu, click link. Modal should close and you remain on page (and browser scrolls to the anchor if you've added an element with the anchor ID).
5. You can test with anchors to other websites, pages, etc to verify that the modal only closes if the exact page and query parameters are met

Screenshots or screencast

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[github-actions]

👋 Thanks for your first Pull Request and for helping build the future of Gutenberg and WordPress, @coreyworrell! In case you missed it, we'd love to have you join us in our Slack community, where we hold regularly weekly meetings open to anyone to coordinate with each other.

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[talldan]

Thanks for this, it fixes the issue for me.

[github-actions]

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Kudos!

[getdave]

@coreyworrell Thanks so much for taking the time here and congrats on your first Gutenberg PR 🥳