feat: add metaData to RouteData

[jrobinson01]

adds an optional metaData object to the route config. This can be used to store additional information about a route. To access the metaData in routeEnter (or anywhere you have a reference to the router) use something like:

const destinationNode = this.router.routeTree.getNodeByKey(routeId);
this.heading = destinationNode.getValue().metaData.title || '';

[chrisgubbels]

Looks good to me, would you mind adding it to the readme files documentation?

[jrobinson01]

added to the readme and demo app: a238def