Add support for customizable scroll behavior

[stackoverfloweth]

• likely an option set when developer calls createRouter
• given context of to and from, allows user to set scroll position after route is loaded
• scroll position can be specific px value
• possibly set scroll position based on element
• will need to consider how to await elements that are loading from async component
• will need to update docs https://router.kitbag.dev/migrating-vue-router.html

https://developer.mozilla.org/en-US/docs/Web/API/Window/scroll