Add: Invert Binary Tree

[awesee]

No description provided.

[codecov]

Codecov Report

Merging #718 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #718      +/-   ##
==========================================
+ Coverage   99.29%   99.29%   +<.01%     
==========================================
  Files         223      224       +1     
  Lines        2261     2267       +6     
==========================================
+ Hits         2245     2251       +6     
  Misses         16       16

Impacted Files	Coverage Δ
problems/invert-binary-tree/invert_binary_tree.go	100% <100%> (ø)

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