make hooks return a result instead of an option

packages/router/src/error.rs

@@ -0,0 +1,8 @@
+/// Errors that may occur during routing.
+#[derive(Debug, thiserror::Error)]
+pub enum RouterError {
+    /// A hook that needs access to a router was called inside a component, that has no parent
+    /// calling the [`use_router`](crate::hooks::use_router) hook.
+    #[error("component needing access not inside router")]
+    NotInsideRouter,
+}