**Background:**
To help users explore templates and find the right one for their intended use, we will replace the close button with a back button in the TemplateDialog once a template has been selected from search results ({T272354}). This only applies when inserting a new template. With this ticket, we will also add a warning message that will warn users about data loss if they have entered data into a selected template.
**Requirements**
[] Add warning about data loss when clicking the back button after having added data.
[] Use #OOUI component from `OO.ui.ProcessDialog`
[] Title:"Remove template?" Error message:"Going back will remove this template and any data you have input. You can then choose a different template. This action is not reversible."
[] Button options: "Cancel" and "Remove template."
[] When no data has been entered, show no warning.
**Mocks**
Related tickets:
- Prototyping ticket: {260887}