add html5 required attribute to string inputs

wcs/qommon/form.py

@@ -635,6 +635,7 @@ class StringWidget(QuixoteStringWidget):
     def render_content(self):
         attrs = {'id': 'form_' + self.get_name_for_id()}
         if self.required:
+            attrs['required'] = 'required'
             attrs['aria-required'] = 'true'
         if getattr(self, 'prefill_attributes', None) and 'autocomplete' in self.prefill_attributes:
             attrs['autocomplete'] = self.prefill_attributes['autocomplete']