[Example] Add Uniswap-V2 example

[codecov[bot]]

Codecov Report

Merging #123 (debab56) into master (fa0dd3a) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #123   +/-   ##
=======================================
  Coverage   66.47%   66.47%           
=======================================
  Files          98       98           
  Lines       13679    13679           
  Branches     2041     2041           
=======================================
  Hits         9093     9093           
  Misses       3567     3567           
  Partials     1019     1019           

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[lgtm-com[bot]]

This pull request introduces 7 alerts when merging debab56e86790fd66bed38b39199960c1ae12bc5 into fa0dd3a588f02f4069736248e79f57d00df5061f - view on LGTM.com

new alerts:

• 4 for Unused import
• 2 for 'import *' may pollute namespace
• 1 for Unused local variable