Add additional kwargs for pytorch_lightning Trainer

[martins0n]

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• Did you read the contribution guide?
• Did you update the docs? We use Numpy format for all the methods and classes.
• Did you write any new necessary tests?
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Type of Change

• Examples / docs / tutorials / contributors update
• Bug fix (non-breaking change which fixes an issue)
• Improvement (non-breaking change which improves an existing feature)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

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[codecov-commenter]

Codecov Report

Merging #540 (9f86088) into master (a2393b4) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #540      +/-   ##
==========================================
+ Coverage   87.49%   87.51%   +0.02%     
==========================================
  Files         118      118              
  Lines        5742     5752      +10     
==========================================
+ Hits         5024     5034      +10     
  Misses        718      718              

Impacted Files	Coverage Δ
etna/models/nn/deepar.py	100.00% <100.00%> (ø)
etna/models/nn/tft.py	100.00% <100.00%> (ø)

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