erp5_interface_post: add interface_post_workflow on Post-type portal_types

bt5/erp5_interface_post/PortalTypeWorkflowChainTemplateItem/workflow_chain_type.xml

 <workflow_chain>
  <chain>
   <type>Internet Message Post</type>
-  <workflow>edit_workflow</workflow>
+  <workflow>edit_workflow, interface_post_workflow</workflow>
  </chain>
  <chain>
   <type>Letter Post</type>
-  <workflow>edit_workflow</workflow>
+  <workflow>edit_workflow, interface_post_workflow</workflow>
  </chain>
 </workflow_chain>
\ No newline at end of file

bt5/erp5_interface_post/bt/template_portal_type_workflow_chain_list

 Internet Message Post | edit_workflow
-Letter Post | edit_workflow
+Internet Message Post | interface_post_workflow
\ No newline at end of file
+Letter Post | edit_workflow
+Letter Post | interface_post_workflow
\ No newline at end of file