Add example project for koa

[Swechhya]

Add a new example project for koa.

Resolves #17

[kabirbaidhya]

@Swechhya Thanks for contributing 💯 👍.

Can you update the PR description to provide some details and the changes you made? There are few comments please do resolve them and it should be mergable 🎉.

[codecov-io]

Codecov Report

Merging #36 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #36   +/-   ##
=======================================
  Coverage   86.61%   86.61%           
=======================================
  Files           5        5           
  Lines         142      142           
  Branches       24       24           
=======================================
  Hits          123      123           
  Misses         15       15           
  Partials        4        4

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[kabirbaidhya]

@Swechhya Few more formatting and indentation fixes. You can also run eslint --fix which will resolve most of these issues.

Additionally, we've defined to only use single quotes in eslint. This should also be resolved once you do eslint --fix.

[kabirbaidhya]

@Swechhya Can you also add a link to the example in the main README under Sample Projects section here - https://github.com/leapfrogtechnology/async-store#sample-projects?

Everything else looks good. Thanks.