text: Title: [DOCS] Add bayesian methods to GMM density page. 
  Body: As mentioned https://github.com/koaning/scikit-lego/issues/608#issuecomment-1900005415, we only mention the bayesian GMM classifier in the [API docs](https://koaning.github.io/scikit-lego/api/mixture/). It would be good to add a paragraph/image to the [user guide](https://koaning.github.io/scikit-lego/user-guide/mixture-methods/) as well. 