doc: Add Common Coding Style Guide.
doc: Add Common Coding Style Guide.

yona-projects/yona,yona-projects/yona,naver/yobi,bloodybear/yona,ahb0327/yobi,ihoneymon/yobi,ihoneymon/yobi,naver/yobi,doortts/forked-for-history,brainagenet/yobi,naver/yobi,violetag/demo,doortts/fork-yobi,ahb0327/yobi,ahb0327/yobi,brainagenet/yobi,ihoneymon/yobi,yona-projects/yona,bloodybear/yona,Limseunghwan/oss,doortts/fork-yobi,ChangsungKim/TestRepository01,doortts/forked-for-history,doortts/fork-yobi,oolso/yobi,ChangsungKim/TestRepository01,doortts/fork-yobi,yona-projects/yona,oolso/yobi,oolso/yobi,violetag/demo,Limseunghwan/oss,bloodybear/yona,brainagenet/yobi,doortts/forked-for-history,bloodybear/yona,Limseunghwan/oss