pre-commit: Add codespell to look for typos

[cclauss]

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Motivation

Please describe the motivation of this PR and the goal you want to achieve through this PR.

Modification

Please briefly describe what modification is made in this PR.

BC-breaking (Optional)

Does the modification introduce changes that break the backward-compatibility of the downstream repos?
If so, please describe how it breaks the compatibility and how the downstream projects should modify their code to keep compatibility with this PR.

Use cases (Optional)

If this PR introduces a new feature, it is better to list some use cases here, and update the documentation.

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, like MMDet or MMCls.
4. The documentation has been modified accordingly, like docstring or example tutorials.

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

Merging #6099 (9510e02) into master (3e7d7e4) will increase coverage by 0.07%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #6099      +/-   ##
==========================================
+ Coverage   61.45%   61.52%   +0.07%     
==========================================
  Files         304      311       +7     
  Lines       23855    24569     +714     
  Branches     3942     4100     +158     
==========================================
+ Hits        14659    15115     +456     
- Misses       8414     8648     +234     
- Partials      782      806      +24     

Flag	Coverage Δ
unittests	61.49% <ø> (+0.06%)	⬆️

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

Impacted Files	Coverage Δ
mmdet/models/detectors/yolo.py	50.00% <0.00%> (-33.34%)	⬇️
mmdet/core/bbox/coder/yolo_bbox_coder.py	52.94% <0.00%> (-8.04%)	⬇️
mmdet/core/bbox/samplers/random_sampler.py	75.00% <0.00%> (-5.56%)	⬇️
mmdet/models/dense_heads/rpn_head.py	88.00% <0.00%> (-4.86%)	⬇️
mmdet/models/plugins/dropblock.py	91.89% <0.00%> (-2.40%)	⬇️
mmdet/models/utils/ckpt_convert.py	3.73% <0.00%> (-0.92%)	⬇️
mmdet/models/dense_heads/yolo_head.py	46.66% <0.00%> (-0.92%)	⬇️
mmdet/models/roi_heads/bbox_heads/bbox_head.py	78.87% <0.00%> (-0.75%)	⬇️
mmdet/models/seg_heads/panoptic_fpn_head.py	27.65% <0.00%> (-0.61%)	⬇️
mmdet/models/roi_heads/cascade_roi_head.py	36.92% <0.00%> (-0.25%)	⬇️
... and 24 more

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[ZwwWayne]

Hi @cclauss ,
Thanks for your kind contribution. Would you like to sign the CLA so that we can merge this PR?

[ZwwWayne]

And lint fails.

[ZwwWayne]

Hi @cclauss ,
Thanks for your kind contribution. Could help to sign the CLA so that we cam merge this PR?

Furthermore,

The indentation is not correct. Could you help to fix that?

[AronLin]

#6306 is a follow-up to this work and it is merged. So close this PR.