Update CONTRIBUTING.md
ライセンスヘッダーの修正
(Modification of the license header)
Merge branch 'develop' of https://github.com/OpenTouryoProject/OpenTouryo into develop
ライセンスヘッダーの修正
(Modification of the license header)
Merge branch 'develop' of https://github.com/OpenTouryoProject/OpenTouryo into develop

Conflicts:
	root/programs/C#/Tests/Public.Test/Public.Test.csproj