ssr example extended to highlight hydration

[geonanorch]

The changes introduced in this PR aim at demonstrating what hydration adds to the initial static rendering delivered from the server (in the current version both steps are chained, there is no time to see the difference).

Note: initially I played with the sample in order to demonstrate a bug in @riotjs/ssr, for which I opened PR#34 and thought that I might as well contribute the change back.