Add audobject.Object.short_id

[hagenw]

Closes #32

[codecov[bot]]

Codecov Report

Merging #100 (9a5fcd4) into main (ad35376) will not change coverage. The diff coverage is 100.0%.

Additional details and impacted files

| [Files](https://app.codecov.io/gh/audeering/audobject/pull/100?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=audeering) | Coverage Δ | | |---|---|---| | [audobject/core/object.py](https://app.codecov.io/gh/audeering/audobject/pull/100?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=audeering#diff-YXVkb2JqZWN0L2NvcmUvb2JqZWN0LnB5) | `100.0% <100.0%> (ø)` | |