SIGN IN SIGN UP

Typo updates for README and Contributions (#10025)

### Summary

Pulling in the non 0.6 changes from:

https://github.com/pytorch/executorch/pull/10006
https://github.com/pytorch/executorch/pull/10016

### Test plan
md
J
Jack-Khuu committed
4bd7798263fb1c9453c493793c95a0a7cbf424f9
Parent: 9b697ae
Committed by GitHub <noreply@github.com> on 4/9/2025, 11:38:33 PM