Validate phone number on login
Validate phone number on login

To prevent confusion when accidently inputting mxid or email. Fixes https://github.com/vector-im/riot-web/issues/3637

matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,aperezdc/matrix-react-sdk,aperezdc/matrix-react-sdk,matrix-org/matrix-react-sdk,aperezdc/matrix-react-sdk,matrix-org/matrix-react-sdk,aperezdc/matrix-react-sdk,matrix-org/matrix-react-sdk