Add Yard Material Calculator blueprint

[demi-valerith]

Adds a self-contained Playground demo for the Yard Material Calculator WordPress plugin.

The Blueprint installs the bundled plugin ZIP, activates it, and creates a front page containing both the dynamic Gutenberg block and shortcode in metric and imperial configurations.

Validated locally:

• Blueprint JSON parses and passes Prettier
• bundled ZIP passes unzip -t
• Playground renders both calculator integrations without console errors

[github-actions]

Test using WordPress Playground

The changes in this pull request can be previewed and tested using a WordPress Playground instance.

WordPress Playground is an experimental project that creates a full WordPress instance entirely within the browser.

Some things to be aware of

• All changes will be lost when closing a tab with a Playground instance.
• All changes will be lost when refreshing the page.
• A fresh instance is created each time one of the links below is clicked.

For more details about these limitations and more, check out the Limitations page in the WordPress Playground documentation.

Blueprint previews

• Open yard-material-calculator in WordPress Playground