Need a shared checkstyle

I personally prefer 2 space indent for my projects (please refer Google coding style for more information, I'm following them). So I configured my IDE to do so. Since you repo use default 4 space indent, it will be helpful if you could include a checkstyle.xml for this project so all of contributors can easily share the coding style without merging problem :D. Cheers!

Start by inspecting the repository's existing Java and Android build configuration to determine where a shared checkstyle.xml should live. Use the requested Google coding style with two-space indentation, and consider the work done when contributors can use the shared configuration consistently without formatting conflicts.

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