Using a Custom Backend page doesn't indicates that Kobweb dynamic routes are not supported

[EchoEllet]

Currently, the page Using a Custom Backend
within the docs, doesn't clarify that Kobweb dynamic routes (not API routes or Dynamic API routes) are not supported and needs to be manually implemented within the custom backend (e.g., Ktor server, Spring boot).

This clarification needs to be done in two places:

• https://kobweb.varabyte.com/docs/guides/existing-backend
• https://kobweb.varabyte.com/docs/concepts/foundation/routing#dynamic-routes

This will ensure a successful deployment for Kobweb users to get started quickly without being confused about unexpected issues when using a custom backend.

• Related Epic: Allow Kobweb to work in cases where it doesn't own the server kobweb#22
• Related Usage of IgnoreTrailingSlash is possibly incorrect or not required when hosting the static site on Ktor server #27
• Not directly related 404 Error when serving Kobweb 404 Page on Ktor Server kobweb#676