feat: bundle in CJS and ESM formats

[Belco90]

Checks

• I have read the contributing guidelines.

Changes

• Set up a bundler (tsdown)
• Update package.json fields for CJS and ESM exposed files
• Set up publint for linting the published bundle
• Update type to "module"
• Move CJS code to ESM
• Rename lib/ to src/ to better reflect the folder holds the source code but must be bundled

Context

Closes #900

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.47%. Comparing base (9c78006) to head (8464ca9).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1130      +/-   ##
==========================================
- Coverage   97.48%   97.47%   -0.01%     
==========================================
  Files          49       49              
  Lines        5997     5974      -23     
  Branches     1518     1518              
==========================================
- Hits         5846     5823      -23     
  Misses        149      149              
  Partials        2        2              

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[Copilot]

Pull request overview

This PR modernizes the build infrastructure by converting from CommonJS to ESM format and setting up a bundler (tsdown). The changes enable dual CJS/ESM bundle distribution, improve TypeScript configuration for module preservation, and reorganize the source structure from lib/ to src/ to better distinguish between source code and built artifacts.

Key changes:

• Convert module system from CommonJS (require/module.exports) to ESM (import/export default)
• Update Node.js built-in imports to use node: protocol
• Rename lib/ directory to src/ throughout the codebase
• Configure TypeScript with "module": "preserve" and "noEmit": true for bundler compatibility

Reviewed changes

Copilot reviewed 59 out of 106 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
vitest.setup.ts	New test setup file for typescript-eslint RuleTester
vitest.config.ts	Updated setup file path and coverage directory from lib/ to src/
tsconfig.json	Changed module system to "preserve" with noEmit enabled
tools/generate-configs/utils.ts	Converted to ESM imports, updated dirname handling, changed export to default
tools/generate-configs/index.ts	Updated import paths from lib/ to src/
tests/**/*.test.ts	Updated all test imports from ../lib/ or ../../../lib/ to ../src/ or ../../src/
tests/test-utils.ts	Updated import path to ../src/utils
tests/fake-rule.ts	Updated import path to ../src/create-testing-library-rule
tests/eslint-remote-tester.config.js	Deleted file (removed)
tests/create-testing-library-rule.test.ts	Fixed import path from ./lib/test-utils to ./test-utils
tests/index.test.ts	Updated paths from lib/ to src/ and imports to ESM
src/utils/*.ts	New ESM files with export statements
src/rules/*.ts	New ESM rule files with default exports
src/node-utils/*.ts	New ESM utility files
src/index.ts	Converted to ESM with default export, updated package.json imports
src/create-testing-library-rule/*.ts	New ESM files for rule creation utilities
src/configs/*.ts	Converted config exports from export = to export default

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