Handle invalid routes in Static Site Editor

What does this MR do?

It handles invalid routes in the Static Site Editor VueRouter setup. When a route not supported is detected, VueRouter will redirect to the Home route.

This MR does not deliver all the required changes to implement VueRouter in the editor. For the full list of Merge Requests and a detailed implementation plan, see #213282 (closed).

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content