add Github contributing guidelines
add Github contributing guidelines

- https://github.com/blog/1184-contributing-guidelines

Erol/hanami-router,AlfonsoUceda/router,supriyantomaftuh/router,hanami/router,vyper/router,hanami/router,Erol/hanami-router,supriyantomaftuh/router,lotus/router,theocodes/router,AlfonsoUceda/router,vyper/router,theocodes/router,lotus/router