seed example UI: routing (Load action to/from URL)

[Ivshti]

implement routing in the seed example UI

routing is as easy as dispatching actions: https://seed-rs.org/guide/7, so it should be very easy to do and also serve as an example of how to translate URLs into a Load action

We can also implement conversion to/from URL for the Load action

[Ivshti]

not doing this cause the seed router is kind of crappy (requires server to be serving index.html for all URLs); also there are too many other tasks