Fixes #5

A few implementation notes:

• Updates the playerlist on an interval. For some bizarre reason it is trivial to get the complete list as a client but an event to listen for joins and leaves is not available through Fabric. Solutions I came across involved creating mixins, which is effectively reflection and very prone to breaking on new minecraft versions. Because of that I decided to go for the interval route as it effectively is just some lookups.
• Player skins are handled by the client by fetching them from minecraft.net. In theory it is possible to fetch the textures from the client and send those along. But in practice I had little luck with that due to asynchronous loading of textures and various other factures. It likely would also make the whole operation a bit heavier which in combination with the interval for updates might actually cause some issues. The texture URL is trivial to fetch, so that is send along to the client and the client handles the head creation.