[Docs] Add 1_exist_data_model.md Chinese Version

[DCNSW]

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Motivation

Add 1_exist_data_model.md Chinese version.

Modification

Add 1_exist_data_model.md Chinese version.

BC-breaking (Optional)

Does the modification introduce changes that break the back-compatibility of the downstream repos?
no.

Use cases (Optional)

no.

Checklist

1. Pre-commit or other linting tools are used to fix the potential lint issues.
2. The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
3. If the modification has potential influence on downstream projects, this PR should be tested with downstream projects.
4. The documentation has been modified accordingly, like docstring or example tutorials.

[codecov]

Codecov Report

Merging #746 (bbb634e) into master (1b2e64c) will increase coverage by 0.09%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #746      +/-   ##
==========================================
+ Coverage   48.94%   49.03%   +0.09%     
==========================================
  Files         208      210       +2     
  Lines       15884    15964      +80     
  Branches     2538     2547       +9     
==========================================
+ Hits         7774     7828      +54     
- Misses       7608     7634      +26     
  Partials      502      502              

Flag	Coverage Δ
unittests	49.03% <ø> (+0.09%)	⬆️

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

Impacted Files	Coverage Δ
mmdet3d/models/segmentors/encoder_decoder.py	20.94% <0.00%> (-0.70%)	⬇️
mmdet3d/datasets/pipelines/transforms_3d.py	90.39% <0.00%> (-0.48%)	⬇️
mmdet3d/models/losses/__init__.py	100.00% <0.00%> (ø)
mmdet3d/models/decode_heads/__init__.py	100.00% <0.00%> (ø)
mmdet3d/ops/group_points/group_points.py	31.18% <0.00%> (ø)
mmdet3d/models/decode_heads/pointnet2_head.py	57.14% <0.00%> (ø)
mmdet3d/models/decode_heads/paconv_head.py	43.75% <0.00%> (ø)
...mdet3d/models/losses/paconv_regularization_loss.py	100.00% <0.00%> (ø)
mmdet3d/models/segmentors/base.py	29.78% <0.00%> (+0.89%)	⬆️
mmdet3d/datasets/builder.py	62.06% <0.00%> (+1.35%)	⬆️
... and 1 more

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[Wuziyi616]

Great! I think this PR is ready to merge now @ZwwWayne