bpo-32677: Add .isascii() to str, bytes and bytearray (GH-5342)

diff --git a/Objects/stringlib/ctype.h b/Objects/stringlib/ctype.h
index f054625..fd7b1bd 100644
--- a/Objects/stringlib/ctype.h
+++ b/Objects/stringlib/ctype.h
@@ -23,6 +23,12 @@
 }
 
 static PyObject*
+stringlib_isascii(PyObject *self)
+{
+    return _Py_bytes_isascii(STRINGLIB_STR(self), STRINGLIB_LEN(self));
+}
+
+static PyObject*
 stringlib_isdigit(PyObject *self)
 {
     return _Py_bytes_isdigit(STRINGLIB_STR(self), STRINGLIB_LEN(self));