Add `wp-theme-<name>` and `wp-child-theme-<name>` classes to body tag

[nirajgiriXD]

Description

This PR introduces new classes to the body tag in WordPress themes. The classes wp-theme-<name> and wp-child-theme-<name> (if child theme) are added, where <name> represents the sanitized name of the active theme and child theme, respectively.

Changes Made

• Added wp-theme-<name> class to the body tag for the current theme.
• Added wp-child-theme-<name> class to the body tag for the current theme (if child theme).

Screenshots

• For twentytwentyfour theme

• For a child theme named childtheme having twentytwentyfour as parent theme

Trac ticket: https://core.trac.wordpress.org/ticket/19736

[github-actions[bot]]

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[github-actions[bot]]

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Test this pull request with WordPress Playground.

[carolinan]

If these class names are intended to help plugins with theme specific styles, they also need to be present in the Site Editor. (They are already available in the Customizer preview)

[carolinan]

I checked again, neither of the existing body classes are added in the Site Editor. I am not sure why. It should be treated as a separate issue and not block this update.

[github-actions[bot]]

A commit was made that fixes the Trac ticket referenced in the description of this pull request.

SVN changeset: 59698 GitHub commit: https://github.com/WordPress/wordpress-develop/commit/0f6707de3023234b85e7186fa5cd10ad039d0109

This PR will be closed, but please confirm the accuracy of this and reopen if there is more work to be done.