Add data mappers for divider block

[MAILPOET-2462]

assets/js/src/form_editor/store/blocks_to_form_body.jsx

@@ -74,6 +74,15 @@ export default (blocks) => {
           type: 'submit',
           name: 'Submit',
         };
+      case 'mailpoet-form/divider':
+        return {
+          ...mapped,
+          id: 'divider',
+          type: 'divider',
+          name: 'Divider',
+          static: '0',
+          params: '',
+        };
       default:
         return null;
     }

assets/js/src/form_editor/store/form_body_to_blocks.jsx

@@ -6,7 +6,7 @@ export default (data) => {
   if (!Array.isArray(data)) {
     throw new Error('Mapper expects form body to be an array.');
   }
-  return data.map((item) => {
+  return data.map((item, index) => {
     const mapped = {
       clientId: item.id,
       isValid: true,
@@ -64,6 +64,12 @@ export default (data) => {
           ...mapped,
           name: 'mailpoet-form/submit-button',
         };
+      case 'divider':
+        return {
+          ...mapped,
+          name: 'mailpoet-form/divider',
+          clientId: `divider_${index}`,
+        };
       default:
         return null;
     }