Add npm publishing support for dual JSR and npm distribution

[Copilot]

This PR implements npm publishing capabilities to complement the existing JSR distribution, addressing the community request for npm availability based on takker99/scrapbox-userscript-std#237.

Overview

The package is currently published to JSR (JavaScript Registry) but users have requested npm support for broader ecosystem compatibility. This implementation adds dual publishing while maintaining full backward compatibility with existing JSR users.

Key Changes

🔧 Build Infrastructure

• Dual build system: Added npm package generation using @deno/dnt (Deno Node Transform)
• Complete export mapping: Maps all 3 main modules (rest, userscript, websocket) from deno.jsonc exports to npm package structure
• Format support: Generates both ESM and TypeScript definitions for maximum Node.js compatibility

🚀 CI/CD Integration

• GitHub Actions: Updated publish workflow to deploy to both JSR and npm simultaneously
• Dual jobs: Separate publish-jsr and publish-npm jobs for reliability
• TLS Configuration: Added DENO_TLS_CA_STORE=system to all workflows to ensure reliable JSR package downloads

📚 Documentation & Examples

• Installation options: README now shows both JSR and npm installation methods with badges
• Import examples: Code samples demonstrate both jsr:@cosense/types and @cosense/types import styles
• Usage guide: Clear examples for both Deno and Node.js users
• ⚠️ Node.js Notice: Added experimental support notice explaining compatibility status and providing guidance for users

Package Structure

The npm package maintains the same API surface as JSR:

// JSR (existing)
import type { PageList } from "jsr:@cosense/types/rest";
import type { Scrapbox } from "jsr:@cosense/types/userscript";

// npm (new)  
import type { PageList } from "@cosense/types/rest";
import type { Scrapbox } from "@cosense/types/userscript";

All 3 export paths from the original deno.jsonc configuration are preserved: rest, userscript, and websocket.

Setup Required

To enable npm publishing, add an NPM_TOKEN secret to the repository with an automation token from npmjs.com. The package will be published as @cosense/types (matching the JSR name) when tags are pushed.

Testing

Both JSR and npm build methods have been tested and successfully generate all modules with proper TypeScript definitions:

• ✅ deno task check - Full JSR validation including lint, format, test, and publish dry-run
• ✅ deno task npm:build - Generates complete npm package structure
• ✅ deno task npm:check - Validates npm package for publishing

This implementation provides a seamless experience for users regardless of their preferred package registry while maintaining the existing developer workflow.

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[takker99]

@copilot 1点だけ補足した。対応よろしく。