Consider moving to simple hash router

[paolodamico]

Currently we're using kea router (https://keajs.org/docs/plugins/router) which works great most of the time, but with IPFS we can't properly handle top level routing (see https://docs.fleek.co/hosting/troubleshooting/#my-single-page-application-spa-breaks-when-changing-routes-via-an-ipfs-gatway), this meant we had to introduce some ugly hack to support hash routing for the message retrieval. Instead, might be cleaner to move to a simple hash router instead and stop supporting normal routing.