Add mim to extras_require in setup.py

[zhouzaida]

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Motivation

Add mim to extras_require in setup.py

Modification

Update setup.py

BC-breaking (Optional)

No

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 MMDet3D.
4. The documentation has been modified accordingly, like docstring or example tutorials.

[codecov]

Codecov Report

Merging #1655 (09fe8d5) into master (60655de) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1655   +/-   ##
=======================================
  Coverage   90.25%   90.25%           
=======================================
  Files         142      142           
  Lines        8476     8476           
  Branches     1428     1428           
=======================================
  Hits         7650     7650           
  Misses        586      586           
  Partials      240      240           

Flag	Coverage Δ
unittests	90.25% <ø> (ø)

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