add `count` attribute for AFOS list service

[codecov[bot]]

Codecov Report

Base: 79.55% // Head: 79.56% // Increases project coverage by +0.01% :tada:

Coverage data is based on head (2ee7303) compared to base (0c359aa). Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #125 +/- ## ========================================== + Coverage 79.55% 79.56% +0.01% ========================================== Files 59 59 Lines 1922 1923 +1 ========================================== + Hits 1529 1530 +1 Misses 393 393 ``` | [Impacted Files](https://codecov.io/gh/akrherz/iem-web-services/pull/125?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=daryl+herzmann) | Coverage Δ | | |---|---|---| | [src/iemws/services/nws/afos/list.py](https://codecov.io/gh/akrherz/iem-web-services/pull/125?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=daryl+herzmann#diff-c3JjL2llbXdzL3NlcnZpY2VzL253cy9hZm9zL2xpc3QucHk=) | `100.00% <ø> (ø)` | | | [src/iemws/models/afos/list.py](https://codecov.io/gh/akrherz/iem-web-services/pull/125?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=daryl+herzmann#diff-c3JjL2llbXdzL21vZGVscy9hZm9zL2xpc3QucHk=) | `100.00% <100.00%> (ø)` | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=daryl+herzmann). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=daryl+herzmann)

:umbrella: View full report at Codecov.
:loudspeaker: Do you have feedback about the report comment? Let us know in this issue.