[2.x] add types to useForm in Login.tsx

[joelbutcher]

This PR adds type definitions to the useForm props in Login.tsx for the React Typescript stack, which fixes the problem with these recent tests failing

[taylorotwell]

Hey there! We are rebuilding our starter kits now, so will address any needs there. We should have them out in ~4 weeks.

[joelbutcher]

Hey @taylorotwell I appreciate that you and the team are shifting focus for starter kits, but in the meantime this is currently causing my test pipelines to fail for Socialstream as I try as best I can to follow the files that are published by Laravel (to avoid making too many changes if someone installs Breeze, commit it, then add Socialstream later in a different commit).

If this is a hard "no", I'll just override this in my packages stub files to get my tests passing 👍