add eslint & ci

[dale-wahl]

Adding automated linting and testing to the repository. Hoping to catch undefined global references in extension scripts and ensuring code quality for both our code and the LLM generated code. The main changes include adding a GitHub Actions workflow for CI, integrating ESLint with a custom configuration, and centralizing the discovery of global names used across scripts and tests.

Continuous integration and automation:

• Added .github/workflows/ci.yml to run tests and linting on every push and pull request, to ensure missing helper functions and similar bugs are caught early, especially for the auto-generated map_item functions.

Linting infrastructure:

• Introduced eslint.config.mjs with a configuration that enables the no-undef rule for extension scripts and modules, using a dynamically generated list of global names to avoid false positives.
• Updated tests/package.json to add scripts for running ESLint and included necessary dependencies (eslint, globals).

Global name discovery and sharing:

• Added tests/lib-globals.cjs, which extracts global helper names from js/lib.js and js/zs-background.js, and exposes them for both the test setup and ESLint configuration.
• Refactored tests/setup-globals.cjs to use the shared global name list from lib-globals.cjs