No event triggered when converting content page to another type

Description

Steps to reproduce

1. Create a Standard page.
2. Go to Admin > Content Type > Convert Pages.
3. Convert the page to another type, for example, Product page.

Expected: After the page is converted, an event is triggered so other modules can react, for example reindex it automatically.
Actual: There is no firing event

Fix New event, PagesConverted, added to PageTypeConverter.