This allows hovering on keywords that refer to deduced types.
This should cover most useful cases. Not covered:
- auto template parameters: Since this can be instantiated with many types,
it would not be practical to show the types.
- Structured binding: This could be done later to show multiple deduced types
in the hover.
- auto:: (part of concepts): Outside the scope of this patch.
Signed-off-by: Marc-Andre Laperle <firstname.lastname@example.org>