Compatibility with Tailwind 4.0.0-beta.5 and newer

[TobyPerplex]

Hi, I absolutely love this package and use it in all my projects. I also use Tailwind in all my projects. postcss-advanced-variables and Tailwind up to 4.0.0-beta.4 work perfectly together. However, since they've released beta.5 this is no longer the case. I've opened an issue about it here: tailwindlabs/tailwindcss#15361

In the discussion, one of the Tailwind maintainers says that in order for these packages to work together again postcss-advanced-variables should be ported to use a Once visitor. Is this something you would be willing to change/implement? Maybe as a boolean/parameter in the options?