Predictable Teleport target

[hinogi]

It would be great if there would be an option to set the Teleport target manually instead of always going with body. In testing environments that for example start with the vue app mount point it is often difficult to work with Teleports when you are not familiar with them. Also, the dynamic nature makes some cached HTMLElements stale or unusable. For example if you use within(canvasElement) in storybook you might find the Teleports once but not twice since the create/destroy will also give a different id.