[FF64] Fix Backspace in phone number input

src/pages/pageSignIn.ts

@@ -306,7 +306,7 @@ let onFirstMount = () => {
     //console.log('keypress', this.value);
     if(!btnNext.style.visibility &&/* this.value.length >= 9 && */ e.key === 'Enter') {
       return onSubmit();
-    } else if(/\D/.test(e.key) && !(e.metaKey || e.ctrlKey) && !(e.key === '+' && e.shiftKey/*  && !this.value */)) {
+    } else if(/\D/.test(e.key) && !(e.metaKey || e.ctrlKey) && e.key !== 'Backspace' && !(e.key === '+' && e.shiftKey/*  && !this.value */)) {
       e.preventDefault();
       return false;
     }