Passed to SubmitButton by a form, usually inside FormActions.
children: ReactNode
optional
pendingLabel: ReactNode
Replaces the label while the form is submitting, such as "Saving…".
optional
disabled: boolean
Disables the button, which is disabled while submitting anyway.
optional
className: string
Replaces the btn-primary class.
optional
aria-label: string
Names an icon-only button, such as "✓".