DOC: add lightgbm.rst at doc/source/libraries/xorbits_train

[traderbxy]

What do these changes do?

add lightgbm.rst at doc/source/libraries/xorbits_train by following the code style on doc/source/libraries/xorbits_data/numpy.rst

Related issue number

714

[codecov[bot]]

Codecov Report

Merging #744 (6e39753) into main (f67ffd4) will decrease coverage by 11.33%. The diff coverage is n/a.

@@             Coverage Diff             @@
##             main     #744       +/-   ##
===========================================
- Coverage   93.58%   82.25%   -11.33%     
===========================================
  Files        1058     1058               
  Lines       79780    79780               
  Branches    16504    16504               
===========================================
- Hits        74659    65622     -9037     
- Misses       3446    11889     +8443     
- Partials     1675     2269      +594     

Flag	Coverage Δ
unittests	82.12% <ø> (-11.35%)	:arrow_down:

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see 176 files with indirect coverage changes