Register new payment methods in the documentation
Currently these [payment methods](https://github.com/haveno-dex/haveno-docs/tree/master/docs/the-project/payment-methods) are documented by @nihilist001 but not registered in [mkdocs.yml](https://github.com/haveno-dex/haveno-docs/blob/master/mkdocs.yml) to be published with the docs.