Add leakcanary lib to sample app for memory leak detection

[codecov-commenter]

Codecov Report

Merging #108 into master will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #108   +/-   ##
=======================================
  Coverage   67.25%   67.25%           
=======================================
  Files          31       31           
  Lines        1069     1069           
  Branches       91       91           
=======================================
  Hits          719      719           
  Misses        292      292           
  Partials       58       58           

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[yayaa]

Thank you.