Add object detection docs

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: junjiejiangjjj

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[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.01 :tada:

Comparison is base (f36ca23) 75.81% compared to head (b7f9b6c) 75.82%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2623 +/- ## ========================================== + Coverage 75.81% 75.82% +0.01% ========================================== Files 399 400 +1 Lines 20690 20699 +9 Branches 2754 2754 ========================================== + Hits 15686 15695 +9 Misses 4116 4116 Partials 888 888 ``` | [Impacted Files](https://app.codecov.io/gh/towhee-io/towhee/pull/2623?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=towhee-io) | Coverage Δ | | |---|---|---| | [towhee/runtime/hub\_ops/object\_detection.py](https://app.codecov.io/gh/towhee-io/towhee/pull/2623?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=towhee-io#diff-dG93aGVlL3J1bnRpbWUvaHViX29wcy9vYmplY3RfZGV0ZWN0aW9uLnB5) | `100.00% <100.00%> (ø)` | | | [towhee/runtime/hub\_ops/operator\_parser.py](https://app.codecov.io/gh/towhee-io/towhee/pull/2623?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=towhee-io#diff-dG93aGVlL3J1bnRpbWUvaHViX29wcy9vcGVyYXRvcl9wYXJzZXIucHk=) | `100.00% <100.00%> (ø)` | |

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[Chiiizzzy]

/lgtm