[Feature] Add adjust sharpness

[LXXXXR]

Hi,
In this pull request, adjust_sharpness is added for data augmentation. Pls kindly take a look. Thx.

[codecov]

Codecov Report

Merging #864 (bc8d466) into master (27e9ede) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #864      +/-   ##
==========================================
+ Coverage   66.46%   66.49%   +0.03%     
==========================================
  Files         145      145              
  Lines        8781     8790       +9     
  Branches     1599     1600       +1     
==========================================
+ Hits         5836     5845       +9     
  Misses       2629     2629              
  Partials      316      316              

Flag	Coverage Δ
unittests	66.49% <100.00%> (+0.03%)	⬆️

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Impacted Files	Coverage Δ
mmcv/image/__init__.py	100.00% <ø> (ø)
mmcv/image/photometric.py	100.00% <100.00%> (ø)

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[ZwwWayne]

LGTM