ZIP-0: renames npm package to use the ziptax org

[ericlakich]

This pull request updates the package name from ziptax to @ziptax/node-sdk throughout the codebase and documentation, and removes the release announcement step from the GitHub Actions publish workflow. These changes help standardize the package naming, improve clarity for users, and simplify the release process.

Package name and documentation updates:

• Changed all references of the package name from ziptax to @ziptax/node-sdk in README.md, including installation instructions, import statements, and npm badge links. [1] [2] [3] [4]
• Updated the project name and package name in docs/spec.yaml to @ziptax/node-sdk. [1] [2]
• Updated the name and version fields in package.json to reflect the new package name and version bump.

CI/CD workflow changes:

• Removed the "Create release announcement" step from the .github/workflows/publish.yml workflow, simplifying the release process.