Upgrade Reagent

[soyPabloG]

The current version of Reagent is 1.2.0, so I bring oz up to date (required in a project I'm currently working on).

Two "important" changes have emerged:

• reagent.dom/dom-node is now deprecated, as React introduced the use of refs to obtain the DOM node of the components. Adjustments are based on: https://github.com/reagent-project/reagent/blob/master/doc/FAQ/UsingRefs.md

• In React 18, ReactDOM.render is no longer supported. So I adjust app.cljs following the next example: https://stackoverflow.com/a/71710646