Added the 'Optional' extra require in setup.py

[danielbraun89]

Motivation

Without it, users who are used to install mmlab packages will automatically add the "optional" extra and will encounter a pip error

Modification

Added the missing extra of "optional" as seen in other MM repos as mmaction2 (https://github.com/open-mmlab/mmaction2/blob/master/setup.py#L193) and mmdetection (https://github.com/open-mmlab/mmdetection/blob/master/setup.py#L216)

[CLAassistant]

All committers have signed the CLA.

[liqikai9]

@danielbraun89 Thanks a lot for your contribution! We will review the PR ASAP.
Please sign the CLA so that we can proceed the code merging.

[liqikai9]

Hi @danielbraun89 , do you have any update on this PR? Could you please sign the CLA? So that we can proceed with the code merging

[codecov]

Codecov Report

Merging #1491 (b99333f) into master (afb37d4) will decrease coverage by 0.27%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1491      +/-   ##
==========================================
- Coverage   84.47%   84.20%   -0.28%     
==========================================
  Files         236      236              
  Lines       20036    20039       +3     
  Branches     3602     3603       +1     
==========================================
- Hits        16925    16873      -52     
- Misses       2231     2270      +39     
- Partials      880      896      +16     

Flag	Coverage Δ
unittests	84.20% <ø> (-0.18%)	⬇️

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

Impacted Files	Coverage Δ
mmpose/models/utils/misc.py	71.42% <0.00%> (-28.58%)	⬇️
mmpose/utils/setup_env.py	72.72% <0.00%> (-27.28%)	⬇️
mmpose/datasets/builder.py	69.73% <0.00%> (-9.22%)	⬇️
mmpose/datasets/pipelines/shared_transform.py	75.53% <0.00%> (-8.16%)	⬇️
mmpose/models/utils/tcformer_utils.py	79.65% <0.00%> (-3.44%)	⬇️
mmpose/datasets/pipelines/top_down_transform.py	75.88% <0.00%> (-1.09%)	⬇️
mmpose/apis/inference_3d.py	76.64% <0.00%> (-0.94%)	⬇️
mmpose/apis/inference_tracking.py	61.71% <0.00%> (+0.30%)	⬆️

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[yaqi0510]

danielbraun89，您好！您在MMPose项目中给我们提的PR非常重要，感谢您付出私人时间帮助改进开源项目，相信很多开发者会从你的PR中受益。
我们非常期待与您继续合作，OpenMMLab专门成立了贡献者组织MMSIG，为贡献者们提供开源证书、荣誉体系和专享好礼，可通过添加微信：openmmlabwx 联系我们（请备注mmsig+GitHub id），由衷希望您能加入！

Hi @danielbraun89 ！First of all, we want to express our gratitude for your significant PR in the MMPose project. Your contribution is highly appreciated, and we are grateful for your efforts in helping improve this open-source project during your personal time. We believe that many developers will benefit from your PR.

We would also like to invite you to join our Special Interest Group (SIG) private channel on Discord, where you can share your experiences, ideas, and build connections with like-minded peers. To join the SIG channel, simply message moderator— OpenMMLab on Discord or briefly share your open-source contributions in the #introductions channel and we will assist you. Look forward to seeing you there! Join us ：https://discord.gg/raweFPmdzG

If you have WeChat account，welcome to join our community on WeChat. You can add our assistant ：openmmlabwx. Please add "mmsig + Github ID" as a remark when adding friends：）
Thank you again for your contribution❤