Add Easypanel installation instructions

[serban-alexandru]

After reviewing our past PR (#202), we've made some changes to comply with your requests:

• separated the "server" from "worker";
• added a variable number of replicas for workers.

This is our template at the moment: https://github.com/easypanel-io/templates/blob/main/templates/windmill/index.ts

[rubenfiszel]

Thanks, we would not make it an item on our menu for now but will list it in the self-host page as third party providers in a collapsable. We will take over the PR asap. Thank you for the contribution