Add customized updater tutorial

[SuX97]

Fixes #179

[codecov]

Codecov Report

Merging #181 into master will decrease coverage by 0.10%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #181      +/-   ##
==========================================
- Coverage   85.87%   85.77%   -0.11%     
==========================================
  Files          77       77              
  Lines        4849     4849              
  Branches      765      765              
==========================================
- Hits         4164     4159       -5     
- Misses        559      561       +2     
- Partials      126      129       +3     

Flag	Coverage Δ
#unittests	85.77% <0.00%> (-0.11%)	⬇️

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Impacted Files	Coverage Δ
mmaction/models/backbones/resnet_tin.py	19.85% <0.00%> (ø)
mmaction/core/evaluation/accuracy.py	92.30% <0.00%> (-2.57%)	⬇️

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[dreamerlin]

Remember to update the changelog.md