Add css needed by frontend to render the new badge

[pls78]

Context

Summary

This PR can be summarized in the following changelog entry:

• Fixes an unreleased bug where the New badge in the admin bar Yoast Upgrade button would be rendered incorrectly.
• Adds a margin between the Learn more string and the arrow in the Plans page cards' Learn more button.

Relevant technical choices:

• N/A

Test instructions

Test instructions for the acceptance test before the PR gets merged

This PR can be acceptance tested by following these steps:

• Activate Premium
• Go to your blog frontend and check the the New badge in the admin bar Yoast Upgrade button conforms to the Figma design
• Go to Yoast SEO -> Plans
• Verify the Learn morestring and the arrow in the Learn more buttons are spaced like in the Figma design

Relevant test scenarios

• Changes should be tested with the browser console open
• Changes should be tested on different posts/pages/taxonomies/custom post types/custom taxonomies
• Changes should be tested on different editors (Default Block/Gutenberg/Classic/Elementor/other)
• Changes should be tested on different browsers
• Changes should be tested on multisite

Test instructions for QA when the code is in the RC

• QA should use the same steps as above.

Impact check

This PR affects the following parts of the plugin, which may require extra testing:

• N/A

Other environments

• This PR also affects Shopify. I have added a changelog entry starting with [shopify-seo], added test instructions for Shopify and attached the Shopify label to this PR.

Documentation

• I have written documentation for this change. For example, comments in the Relevant technical choices, comments in the code, documentation on Confluence / shared Google Drive / Yoast developer portal, or other.

Quality assurance

• I have tested this code to the best of my abilities.
• During testing, I had activated all plugins that Yoast SEO provides integrations for.
• I have added unit tests to verify the code works as intended.
• If any part of the code is behind a feature flag, my test instructions also cover cases where the feature flag is switched off.
• I have written this PR in accordance with my team's definition of done.
• I have checked that the base branch is correctly set.

Innovation

• No innovation project is applicable for this PR.
• This PR falls under an innovation project. I have attached the innovation label.
• I have added my hours to the WBSO document.

Fixes #22589

[thijsoo]

We can do this with tailwind styles.

[thijsoo]

I think its worth it to change as many styles to the tailwind ones to be consistent.

[thijsoo]

CR + ACC 👍