Add docs for product variations list endpoint new parameters

[albarin]

Adds documentation for the REST endpoint introduced in woocommerce/woocommerce#54235

Testing steps

1. Run the build script found in the root of this repo: ./build.sh
2. Find the build directory created by the script, and the index.html file within. Load that file in your web browser.
3. Click on the Product variations > List all product variations item in the left-side menu. Read the text and the code examples and make sure it all makes sense and there aren't any typos.

⚠️ We should not merge this until 9.7 is released ⚠️