Annotate types of attrs attributes

[sscherfke]

Is your feature request related to a problem? Please describe.
autodoc-typehint adds type hints to attributes of normal classes but not to attributes of attrs classes.

Describe the solution you'd like
Type hints are shown for attrs classes, too.

Describe alternatives you've considered
Manually hacking around the issue.

Additional context
Output for normal classes:

Output for attrs classes:

[gaborbernat]

A PR for this would be welcome.