Add Usesend but havent tested it just yet

packages/backend/convex/custom/auth/index.ts

@@ -1,3 +1,4 @@
 export { validatePassword } from './password/validate';
 export { Entra } from './providers/entra';
 export { Password } from './providers/password';
+export { Usesend } from './providers/usesend';