Workflows: add mark as read/unread actions

Fixed: twpowertools:147
Change-Id: I6bb2363256cfd2a0ff3aafb4df71f24561576b27
diff --git a/src/workflows/manager/shared/actions.js b/src/workflows/manager/shared/actions.js
index 4551f1f..fcf12e1 100644
--- a/src/workflows/manager/shared/actions.js
+++ b/src/workflows/manager/shared/actions.js
@@ -13,9 +13,11 @@
   17: 'Subscribe/unsubscribe to thread',
   18: 'Vote thread',
   19: 'Report thread',
+  20: 'Mark as read',
+  21: 'Mark as unread',
 };
 
-export const kSupportedActions = new Set([6]);
+export const kSupportedActions = new Set([6, 20, 21]);
 
 export const kActionStyles = css`
   .action {