Add AHT20 example code

[SoulKa]

Add example code for AHT20 to appear in the docs.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (872d025) 61.4% compared to head (8503564) 61.4%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #71 +/- ## ===================================== Coverage 61.4% 61.4% ===================================== Files 67 67 Lines 7567 7567 ===================================== + Hits 4644 4647 +3 + Misses 2760 2757 -3 Partials 163 163 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[SoulKa]

Will add doc.go, too

[maruel]

Thanks!