[3.x] Add a single `Hyde::registerPage($page)` API

[emmadesilva]

Add a single Hyde::registerPage($page) API

Registering a page after kernel boot currently requires two coordinated calls:

Hyde::pages()->addPage($page);
Hyde::routes()->addRoute(new Route($page));

Add a convenience API such as:

Hyde::registerPage($page);

It should register both the page and its route, reducing boilerplate and preventing pages from being added without a corresponding route.