add redirectTo parameter when not signed in

[chrtze]

to redirect to the page that you were looking for, we should add a redirectTo parameter to the signup/signin form so that we can redirect after successfully authentication. example:

-> pro.reactflow.dev/examples/react/auto-layout -> not signed in -> pro.reactflow.dev/signin?redirectTo=/examples/react/auto-layout -> enter credentials -> pro.reactflow.dev/examples/react/auto-layout