Add folder and files for Twenty Twenty-Five

[carolinan]

Trac ticket:
https://core.trac.wordpress.org/ticket/62103

This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.

[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.

Core Committers: Use this line as a base for the props when committing in SVN:

Props poena, peterwilsoncc.

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

[github-actions]

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[peterwilsoncc]

This looks good to me for an initial merge.

I've noticed the following, none of which I think are blockers:

• a number of sample text strings in various files will need to be made translatable
• I've pushed a minor fix for some commenting standards that will need to merged upstream, see 6c07c1e

I've updated the default theme constant and verified it works.

The PHP Unit test failures are unrelated.

A props list will need to be generated from https://github.com/WordPress/twentytwentyfive/ for the core commit.

[peterwilsoncc]

Merged r59146 / a268866

Thank you!