update readme

Author: gperouffe

README.md

@@ -75,10 +75,10 @@ export class YourModule { }
 (saveFunction)="save($event)" 
 (deleteFunction)="deletePanel()" 
 (deleteCardFunc)="deleteCard($event)"
- [addButtonText]="'Add card'"
- [saveButtonText]="'Save panel'"
- [deleteButtonText]="'Delete panel'"
- [deleteCardButtonText]="'Delete card'">
+[addButtonText]="'Add card'"
+[saveButtonText]="'Save panel'"
+[deleteButtonText]="'Delete panel'"
+[deleteCardButtonText]="'Delete card'">
 </gridStack>
 ```
 #### Second mode