feat: implement strategy for optional peer deps

[sjinks]

Adopt a hybrid dependency model aligning with ESLint shareable config and plugin packaging guidance. This allows consumers to opt in to optional framework/tooling packages (TypeScript, React, Jest, Prettier) while keeping runtime-required parser/plugin packages reliable and always installed.

Changes:

• Move typescript, react, jest, and prettier from devDependencies to peerDependencies and mark as optional via peerDependenciesMeta
• Expand is-package-installed() to detect optional peers in consumer package.json, enabling graceful handling in library contexts
• Add utils/load-optional-config.js for guarded loading of optional config stacks, preventing MODULE_NOT_FOUND crashes when optional peers are absent
• Refactor configs/recommended.js to use guarded loader for conditional TypeScript, testing, React, and Prettier config composition
• Create public init.js entrypoint to preload optional packages for consumers requiring upfront resolution
• Add comprehensive unit test coverage for guarded loader behavior

Package classification:

• Keep in dependencies: all runtime-loaded parsers, plugins, resolvers, eslint-config-prettier, globals, find-package-json, typescript-eslint
• Add as optional peers: typescript, react, jest, prettier
• Keep as peerDependency: eslint

Benefits:

• Consumers only install framework/tooling packages they actually use
• Backward compatible: existing consumers with all packages installed continue working without changes
• Clearer intent: optional ecosystem boundaries are explicit
• Low setup friction: recommended config still works with minimal consumer configuration
• Reliable defaults: parser/plugin stack remains guaranteed available

Documentation:

• Update README to clarify optional peer behavior and usage patterns
• Document init entrypoint for consumers requiring preloading
• Add guidance for JS-only consumers and framework-specific setups

[Copilot]

Pull request overview

This PR updates the package/dependency model to support optional peer dependencies (TypeScript, React, Jest, Prettier) and introduces guarded config loading so consumers can opt into integrations without runtime crashes when those optional packages are absent.

Changes:

• Add a guarded optional-config loader and refactor recommended config composition to use it.
• Expand package detection to consider peerDependencies in the consumer’s package.json.
• Update packaging/docs and add unit tests + an init.js entrypoint for preloading optional stacks.

Reviewed changes

Copilot reviewed 7 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
utils/load-optional-config.js	New helper to conditionally load optional config stacks and avoid hard crashes on missing modules.
utils/is-package-installed.js	Extends dependency detection to include peerDependencies in the resolved parent package.json.
configs/recommended.js	Refactors recommended config to compose optional stacks via the guarded loader.
init.js	Adds an entrypoint that attempts to preload optional config stacks when the corresponding optional peer is present.
tests/load-optional-config.js	Adds unit tests for guarded-loader behavior.
package.json	Moves TypeScript/React/Jest/Prettier to optional peer dependencies (via peerDependenciesMeta).
package-lock.json	Updates lockfile metadata to reflect new peer dependency configuration.
README.md	Documents optional peer behavior and the init entrypoint usage.

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[Copilot]

Pull request overview

Copilot reviewed 7 out of 8 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 8 out of 9 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 8 out of 9 changed files in this pull request and generated no new comments.