add example-client docker image

[vankichi]

Description

SSIA

Related Issue

Versions

• Vald Version: v1.7.13
• Go Version: v1.23.2
• Rust Version: v1.81.0
• Docker Version: v27.3.1
• Kubernetes Version: v1.31.1
• Helm Version: v3.16.2
• NGT Version: v2.2.4
• Faiss Version: v1.9.0

Checklist

• [x] I have read the CONTRIBUTING document and completed our CLA agreement.
• [x] I have checked open Pull Requests for the similar feature or fixes?

Special notes for your reviewer

Summary by CodeRabbit

• New Features

  • Introduced a new GitHub Actions workflow for automating Docker image builds for the example client.
  • Added support for building and packaging an example client target.
  • New Docker image build targets for the example client have been implemented.

• Improvements

  • Enhanced the Makefile with new variables and functions to streamline the build process for the example client.
  • Updated distance calculation method in configuration for improved feature vector processing.

These changes improve the efficiency and automation of the build and deployment processes for the example client application.