Add link for Japanese translation

Author: mitsuruog

react/README.md

@@ -575,5 +575,6 @@
   - ![pl](https://raw.githubusercontent.com/gosquared/flags/master/flags/flags/shiny/24/Poland.png) **Polish**: [pietraszekl/javascript](https://github.com/pietraszekl/javascript/tree/master/react)
   - ![kr](https://raw.githubusercontent.com/gosquared/flags/master/flags/flags/shiny/24/South-Korea.png) **Korean**: [apple77y/javascript](https://github.com/apple77y/javascript/tree/master/react)
   - ![Br](https://raw.githubusercontent.com/gosquared/flags/master/flags/flags/shiny/24/Brazil.png) **Portuguese**: [ronal2do/javascript](https://github.com/ronal2do/airbnb-react-styleguide)
+  - ![jp](https://raw.githubusercontent.com/gosquared/flags/master/flags/flags/shiny/24/Japan.png) **Japanese**: [mitsuruog/javascript-style-guide](https://github.com/mitsuruog/javascript-style-guide)
 
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