Add ITK documentation PR preview builds

### Description

Add ITK documentation PR preview builds.

### Impact analysis

Whenever a change is made to the ITK documentation, whether it is the Doxygen configuration, the `.dox` Doxygen pages, or the documentation of a class or method, we ignore how things will look like unless a local build is performed or until the changes have been merged. If changes do not have the expected result, this involves more maintenance (reverting commits or more commits, delays, a new PR cycle, which still does not build the documentation, etc.).

### Expected behavior

We should have documentation PR preview builds.

### Actual behavior

No documentation PR preview builds are available: we cannot check the impact of a change unless a local build is done.

### Versions

`master`

### Environment

Any

### Additional Information

Cross-referencing https://github.com/InsightSoftwareConsortium/ITK/pull/4251#pullrequestreview-1661598538.