add helm charts for app-design-center

[jinbaebang]

Description

This PR proposes the addition of new Helm chart samples to support the Application Design Center (ADC). These templates are designed to provide standardized, ready-to-use workload definitions for various GKE environments.

The new samples will be located under the /app-design-center directory and will follow the existing structure found in my fork. The proposed structure is:

/app-design-center
├── ai-inference/
├── enterprise-production/
├── simple-app-multi-region/
└── simple-app-single-region/

Tasks

• The contributing guide has been read and followed.
• The samples added / modified have been fully tested.
• Workflow files have been added / modified, if applicable.
• Region tags have been properly added, if new samples.
• Editable variables have been used, where applicable.
• All dependencies are set to up-to-date versions, as applicable.
• Merge this pull-request for me once it is approved.

[NimJay]

Question: Should we link to https://cloud.google.com/application-design-center/docs/build-on-google-templates instead?

Suggested change

	These samples show how to deploy a Gemma 2 27B model for inference. Visit https://cloud.google.com/kubernetes-engine/docs/ to follow the tutorial.
	These samples show how to deploy a Gemma 2 27B model for inference. Visit https://cloud.google.com/application-design-center/docs/build-on-google-templates to follow the tutorial.

[NimJay]

Question: Should we link to https://cloud.google.com/application-design-center/docs/build-on-google-templates instead?

Suggested change

	These samples show how to deploy a stateless web application for production. Visit https://cloud.google.com/kubernetes-engine/docs/ to follow the tutorial.
	These samples show how to deploy a stateless web application for production. Visit https://cloud.google.com/application-design-center/docs/build-on-google-templates for instructions.

[NimJay]

Question: Should we link to https://cloud.google.com/application-design-center/docs/build-on-google-templates instead?

Suggested change

	These samples show how to deploy a multi-region web application. Visit https://cloud.google.com/kubernetes-engine/docs/ to follow the tutorial.
	These samples show how to deploy a multi-region web application. Visit https://cloud.google.com/application-design-center/docs/build-on-google-templates for instructions.

[NimJay]

Question: Should we link to https://cloud.google.com/application-design-center/docs/build-on-google-templates instead?

Suggested change

	These samples show how to deploy a simple web application in a single region. Visit https://cloud.google.com/kubernetes-engine/docs/ to follow the tutorial.
	These samples show how to deploy a simple web application in a single region. Visit https://cloud.google.com/application-design-center/docs/build-on-google-templates for instructions.

[NimJay]

Praise: Thanks for adding these licenses headers (even in the .tpl files)! :)

[NimJay]

This is very well done! Thank you, @jinbaebang, for these samples. :)

Approved. I just left a few questions about the URLs in the README.mds.

[NimJay]

Praise: Thanks for adding this GitHub Action for testing the Helm charts!