docs: Add CI/CD example for building Argo Workflows. Closes argoproj#…

…8591

This commit introduces a detailed example for implementing CI/CD pipelines to build Argo Workflows using Argo Workflows:

- **CI**: Includes steps for initializing builds via webhook, building the CLI, using Buildkit for image builds, running tests, collecting coverage reports, deploying to a cluster, and executing basic E2E tests.
- **CD**: Covers tagging, updating manifests with kustomize, committing updates, and initiating an Argo CD sync.
- **Pipeline**: Integrates CI and CD jobs with an approval step.

Signed-off-by: Wesley Scholl <[email protected]>