fix: typo in router docs (#790)

src/routes/solid-router/concepts/actions.mdx

@@ -90,7 +90,7 @@ export function MyComponent() {
 ```
 
 Using `useSubmission` leaves the implementation details of how you trigger `echo` up to you.
-Whe handling user inputs, for example, it is better to use a `form` for a multitude of reasons.
+When handling user inputs, for example, it is better to use a `form` for a multitude of reasons.
 
 ## Using forms to submit data