Add modern bundle output option

[dicnunz]

Fixes #182.\n\nIssueHunt bounty: https://issuehunt.io/r/egoist/bili/issues/182\n\n## Summary\n- Add a --modern CLI flag and output.modern config option\n- Build an additional .modern bundle for each requested format\n- Target native ES module browsers for the modern build and preserve modern async syntax\n- Add [modern] filename placeholder support while appending .modern by default\n- Document the CLI usage and add snapshot coverage\n\n## Tests\n- PATH=/Users/nicdunz/.nvm/versions/node/v16.20.2/bin:/opt/homebrew/bin:/opt/homebrew/sbin:/usr/local/bin:/System/Cryptexes/App/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/local/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/appleinternal/bin:/opt/pmk/env/global/bin:/Library/Apple/usr/bin:/Users/nicdunz/.codex/tmp/arg0/codex-arg05z9Jdd:/Users/nicdunz/.nvm/versions/node/v22.22.0/bin:/Users/nicdunz/bin:/Users/nicdunz/.local/bin:/Users/nicdunz/.lmstudio/bin:/opt/homebrew/opt/libpq/bin:/Library/Frameworks/Python.framework/Versions/3.13/bin:/Applications/Codex.app/Contents/Resources yarn test:unit --runInBand\n- PATH=/Users/nicdunz/.nvm/versions/node/v16.20.2/bin:/opt/homebrew/bin:/opt/homebrew/sbin:/usr/local/bin:/System/Cryptexes/App/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/local/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/appleinternal/bin:/opt/pmk/env/global/bin:/Library/Apple/usr/bin:/Users/nicdunz/.codex/tmp/arg0/codex-arg05z9Jdd:/Users/nicdunz/.nvm/versions/node/v22.22.0/bin:/Users/nicdunz/bin:/Users/nicdunz/.local/bin:/Users/nicdunz/.lmstudio/bin:/opt/homebrew/opt/libpq/bin:/Library/Frameworks/Python.framework/Versions/3.13/bin:/Applications/Codex.app/Contents/Resources yarn types\n- PATH=/Users/nicdunz/.nvm/versions/node/v16.20.2/bin:/opt/homebrew/bin:/opt/homebrew/sbin:/usr/local/bin:/System/Cryptexes/App/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/local/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/appleinternal/bin:/opt/pmk/env/global/bin:/Library/Apple/usr/bin:/Users/nicdunz/.codex/tmp/arg0/codex-arg05z9Jdd:/Users/nicdunz/.nvm/versions/node/v22.22.0/bin:/Users/nicdunz/bin:/Users/nicdunz/.local/bin:/Users/nicdunz/.lmstudio/bin:/opt/homebrew/opt/libpq/bin:/Library/Frameworks/Python.framework/Versions/3.13/bin:/Applications/Codex.app/Contents/Resources yarn prettier --check src/babel/preset.ts src/cli.ts src/index.ts src/plugins/babel.ts src/types.ts test/index.test.ts docs/README.md test/fixtures/modern/index.js\n- git diff --check

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IssueHunt Summary

Referenced issues

This pull request has been submitted to:

• #182: Legacy bundles & modern bundles

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[dicnunz]

Revalidated this branch locally on May 13, 2026.

Passed:

• yarn install --frozen-lockfile (completed; optional fsevents native warning ignored by Yarn)
• yarn test:unit --runInBand
• yarn types
• yarn prettier --check src/babel/preset.ts src/cli.ts src/index.ts src/plugins/babel.ts src/types.ts test/index.test.ts docs/README.md test/fixtures/modern/index.js
• git diff --check

The remaining failed Vercel status is the team authorization gate shown in the Vercel comment, not a local test/build failure on this branch.