Update README.md with contribution information

Julien LepillerThu Apr 18 14:25:39+0200 2019

54b501d

nani/app/furiganatextview/src/main/res/values
namelast commitdate
attrs.xmlAdd furiganaMon Apr 15 20:09:48+0200 2019
strings.xmlAdd furiganaMon Apr 15 20:09:48+0200 2019