feat(webapp): explain subname

www/webapp/src/views/CrudList.vue

@@ -128,6 +128,7 @@
                                 :error-messages="c.createErrors"
                                 :required="c.required || false"
                                 :disabled="createInhibited || createDialogSuccess"
+                                :hint="c.hint"
                                 autofocus
                                 @input="clearErrors(c)"
                         />

www/webapp/src/views/CrudListRecord.vue

@@ -48,6 +48,7 @@ export default {
           name: 'item.subname',
           text: 'Subname',
           align: 'left',
+          hint: 'This is only the part in front of your domain. Example: "www"',
           sortable: true,
           value: 'subname',
           readonly: true,