Make repo compliant

[RaphaelVogel]

How to categorize this PR? /area compliance /kind cleanup

What this PR does / why we need it:

• 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
• Deleted NOTICE.md file
• 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-shoot-cert-service/main.go
  • cmd/gardener-extension-shoot-cert-service/app/options.go
  • cmd/gardener-extension-shoot-cert-service/app/app.go
  • test/integration/healthcheck/test.go
  • charts/charts.go
  • charts/gardener-extension-shoot-cert-service/doc.go
  • hack/tools.go
  • imagevector/imagevector.go
  • pkg/cmd/options.go
  • pkg/apis/config/register.go
  • pkg/apis/config/types.go
  • pkg/apis/config/doc.go
  • pkg/apis/config/v1alpha1/register.go
  • pkg/apis/config/v1alpha1/v1alpha1_suite_test.go
  • pkg/apis/config/v1alpha1/defaults_test.go
  • pkg/apis/config/v1alpha1/types.go
  • pkg/apis/config/v1alpha1/defaults.go
  • pkg/apis/config/v1alpha1/doc.go
  • pkg/apis/config/validation/validation_suite_test.go
  • pkg/apis/config/validation/validation.go
  • pkg/apis/config/validation/validation_test.go
  • pkg/apis/service/register.go
  • pkg/apis/service/types.go
  • pkg/apis/service/doc.go
  • pkg/apis/service/install/install.go
  • pkg/apis/service/v1alpha1/register.go
  • pkg/apis/service/v1alpha1/types.go
  • pkg/apis/service/v1alpha1/defaults.go
  • pkg/apis/service/v1alpha1/doc.go
  • pkg/apis/service/validation/validation_suite_test.go
  • pkg/apis/service/validation/validation.go
  • pkg/apis/service/validation/validation_test.go
  • pkg/controller/add.go
  • pkg/controller/actuator.go
  • pkg/controller/config/config.go
  • pkg/controller/healthcheck/add.go
  • pkg/controller/healthcheck/managed_resource_issuer.go
  • test/integration/suites/run_suite_test.go