gptel.el (gptel): When calling `gptel' with a selected region, insert it
into a new session.
gptel-transient.el (gptel--suffix-send-existing,
gptel--suffix-send-new): Transient suffixes available when a region is
selected. These send the text as a prompt in a existing or new gptel
session.
gptel-transient (gptel-send-menu): Add new transient-prefix
`gptel-send-menu' for setting API options for the buffer
and (optionally) sending queries. Various infix options are supported.
2023-03-09: Some transient menus are generated dynamically, which
requires a more recent version of transient than the latest tagged
release. As a result, the dynamic generation code is commented out for
now.
