Summary:
This PR adds the example flipper plugin in swift sample app. Example flipper plugin acts as an example for the plugin authors. The example flipper plugin was already added in an objective c example but the swift sample app didn't have it.
Pull Request resolved: https://github.com/facebook/flipper/pull/329
Reviewed By: jknoxville
Differential Revision: D13085611
Pulled By: priteshrnandgaonkar
fbshipit-source-id: d86cca43e95592ecca8d9991d170e62170b8217b
6e1c1d57f9