fix(webapp): allow _ in CNAME targets

webapp/src/components/Field/RecordCNAME.vue

@@ -2,7 +2,7 @@
 import { helpers } from 'vuelidate/lib/validators';
 import Record from './Record.vue';
 
-const hostname = helpers.regex('hostname', /^((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))[.]?$/);
+const hostname = helpers.regex('hostname', /^((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}])|(([a-zA-Z0-9_-]+\.)+[a-zA-Z]{2,}))[.]?$/);
 const trailingDot = helpers.regex('trailingDot', /[.]$/);
 
 export default {