[Feature] Add tool for converting label studio json result to coco format

[CescMessi]

Motivation

A tool to convert label studio's json annotation results to coco format.

Modification

Add a single python script file.

BC-breaking (Optional)

Use cases (Optional)

python tools/dataset_converters/labelstudio2coco.py config.xml project-1-at-2023-05-13-09-22-91b53efa.json output/result.json

The config.xml is from Labeling Interface in label studio web ui. The content is like that:

<View>
  <KeyPointLabels name="kp-1" toName="img-1">
  	<Label value="person" background="#D4380D"/>
  </KeyPointLabels>
  <PolygonLabels name="polygonlabel" toName="img-1"> 
  	<Label value="person" background="#0DA39E"/>
  </PolygonLabels>
  <RectangleLabels name="label" toName="img-1"> 
  	<Label value="person" background="#DDA0EE"/>
  </RectangleLabels>
  <Image name="img-1" value="$img"/>
</View>

The project-*.json is from Export -> JSON in label studio web ui. The annotation order should be keypoints, rectangle/polygon.

Checklist

Before PR:

• I have read and followed the workflow indicated in the CONTRIBUTING.md to create this PR.
• Pre-commit or linting tools indicated in CONTRIBUTING.md are used to fix the potential lint issues.
• Bug fixes are covered by unit tests, the case that causes the bug should be added in the unit tests.
• New functionalities are covered by complete unit tests. If not, please add more unit tests to ensure correctness.
• The documentation has been modified accordingly, including docstring or example tutorials.

After PR:

• CLA has been signed and all committers have signed the CLA in this PR.

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.03 ⚠️

Comparison is base (65ef573) 82.04% compared to head (de0d7c8) 82.02%.

❗ Current head de0d7c8 differs from pull request most recent head 0be66ca. Consider uploading reports for the commit 0be66ca to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           dev-1.x    #2385      +/-   ##
===========================================
- Coverage    82.04%   82.02%   -0.03%     
===========================================
  Files          233      233              
  Lines        13643    13643              
  Branches      2320     2320              
===========================================
- Hits         11194    11191       -3     
- Misses        1911     1914       +3     
  Partials       538      538              

Flag	Coverage Δ
unittests	82.02% <ø> (-0.03%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
mmpose/structures/bbox/transforms.py	68.70% <ø> (ø)

... and 1 file with indirect coverage changes

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[vansin]

@CescMessi please write a readme in docs/en/dataset_zoo/label_studio.md and docs/zh/dataset_zoo/label_studio.md

[CescMessi]

@CescMessi please write a readme in docs/en/dataset_zoo/label_studio.md and docs/zh/dataset_zoo/label_studio.md

They have been done now.