Make repo compliant

[RaphaelVogel]

How to categorize this PR? /area compliance /kind cleanup /os garden-linux

What this PR does / why we need it:

• Deleted NOTICE.md file
• Updated CONTRIBUTING.md file
• Created/Updated LICENSE file
  • Deleted LICENSE.md file
• Created/Updated .reuse/dep5 file
• Created/Updated LICENSES folder
• Added badge for reuse compliance in README.md file and registered repo with REUSE API
• License/Copyright header replacement for 'non-go' files
  • Makefile
  • hack/update-github-templates.sh
  • hack/update-codegen.sh
• License/Copyright header replacement for 'go' files
  • cmd/gardener-extension-os-gardenlinux/main.go
  • cmd/gardener-extension-os-gardenlinux/app/app.go
  • charts/gardener-extension-os-gardenlinux/doc.go
  • hack/tools.go
  • pkg/gardenlinux/constants.go
  • pkg/apis/memoryonegardenlinux/types.go
  • pkg/apis/memoryonegardenlinux/doc.go
  • pkg/apis/memoryonegardenlinux/install/install.go
  • pkg/apis/memoryonegardenlinux/v1alpha1/register.go
  • pkg/apis/memoryonegardenlinux/v1alpha1/types.go
  • pkg/apis/memoryonegardenlinux/v1alpha1/defaults.go
  • pkg/apis/memoryonegardenlinux/v1alpha1/doc.go
  • pkg/controller/operatingsystemconfig/add.go
  • pkg/controller/operatingsystemconfig/actuator.go
  • pkg/controller/operatingsystemconfig/actuator_test.go
  • pkg/controller/operatingsystemconfig/operatingsystemconfig_suite_test.go
  • pkg/controller/operatingsystemconfig/generator/generator_suite_test.go
  • pkg/controller/operatingsystemconfig/generator/generator.go
  • pkg/controller/operatingsystemconfig/generator/generator_test.go
  • pkg/controller/operatingsystemconfig/generator/gardenlinux/additional_files.go
  • pkg/controller/operatingsystemconfig/generator/gardenlinux/cgroups.go
  • pkg/controller/operatingsystemconfig/generator/testfiles/embed.go
  • pkg/memoryone/values.go
  • pkg/memoryone/constants.go
  • pkg/apis/memoryonegardenlinux/register.go

Additional information To keep this repository compliant, CODEOWNERS must maintain their third party dependencies in the vendor folder using .reuse/dep5 file. To prevent constant maintenance effort, it is highly recommended to remove the vendor folder. In this case no third party dependencies of the vendor folder must be maintained anymore!