Add serving 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: 83.33% and project coverage change: -0.10 :warning:

Comparison is base (4f76c1d) 75.78% compared to head (b2fd2a8) 75.69%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2608 +/- ## ========================================== - Coverage 75.78% 75.69% -0.10% ========================================== Files 387 387 Lines 20545 20595 +50 Branches 2746 2756 +10 ========================================== + Hits 15570 15589 +19 - Misses 4087 4118 +31 Partials 888 888 ``` | [Impacted Files](https://app.codecov.io/gh/towhee-io/towhee/pull/2608?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=towhee-io) | Coverage Δ | | |---|---|---| | [towhee/serve/api\_service.py](https://app.codecov.io/gh/towhee-io/towhee/pull/2608?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=towhee-io#diff-dG93aGVlL3NlcnZlL2FwaV9zZXJ2aWNlLnB5) | `96.00% <ø> (ø)` | | | [towhee/serve/io/bytes\_io.py](https://app.codecov.io/gh/towhee-io/towhee/pull/2608?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=towhee-io#diff-dG93aGVlL3NlcnZlL2lvL2J5dGVzX2lvLnB5) | `100.00% <ø> (ø)` | | | [towhee/serve/io/json\_io.py](https://app.codecov.io/gh/towhee-io/towhee/pull/2608?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=towhee-io#diff-dG93aGVlL3NlcnZlL2lvL2pzb25faW8ucHk=) | `100.00% <ø> (ø)` | | | [towhee/serve/io/ndarray\_io.py](https://app.codecov.io/gh/towhee-io/towhee/pull/2608?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=towhee-io#diff-dG93aGVlL3NlcnZlL2lvL25kYXJyYXlfaW8ucHk=) | `80.55% <ø> (ø)` | | | [towhee/serve/server\_builder.py](https://app.codecov.io/gh/towhee-io/towhee/pull/2608?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=towhee-io#diff-dG93aGVlL3NlcnZlL3NlcnZlcl9idWlsZGVyLnB5) | `0.00% <ø> (ø)` | | | [towhee/serve/io/text\_io.py](https://app.codecov.io/gh/towhee-io/towhee/pull/2608?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=towhee-io#diff-dG93aGVlL3NlcnZlL2lvL3RleHRfaW8ucHk=) | `75.00% <50.00%> (ø)` | | | [towhee/serve/http/server.py](https://app.codecov.io/gh/towhee-io/towhee/pull/2608?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=towhee-io#diff-dG93aGVlL3NlcnZlL2h0dHAvc2VydmVyLnB5) | `88.63% <77.77%> (-8.67%)` | :arrow_down: | | [towhee/serve/grpc/server.py](https://app.codecov.io/gh/towhee-io/towhee/pull/2608?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=towhee-io#diff-dG93aGVlL3NlcnZlL2dycGMvc2VydmVyLnB5) | `90.14% <100.00%> (+5.52%)` | :arrow_up: | ... and [1 file with indirect coverage changes](https://app.codecov.io/gh/towhee-io/towhee/pull/2608/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=towhee-io)

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[Chiiizzzy]

/lgtm