feat: add image-text-to-text models in transformers (#1772)

* feat(dolphin): add dolphin support

Signed-off-by: Georg Heiler <georg.kf.heiler@gmail.com>

* rename

Signed-off-by: Georg Heiler <georg.kf.heiler@gmail.com>

* reformat

Signed-off-by: Georg Heiler <georg.kf.heiler@gmail.com>

* fix mypy

Signed-off-by: Georg Heiler <georg.kf.heiler@gmail.com>

* add prompt style and examples

Signed-off-by: Michele Dolfi <dol@zurich.ibm.com>

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Signed-off-by: Georg Heiler <georg.kf.heiler@gmail.com>
Signed-off-by: Michele Dolfi <dol@zurich.ibm.com>
Co-authored-by: Michele Dolfi <dol@zurich.ibm.com>