feat(npm): Add npm package distribution support

Added npm package wrapper to enable installation via npm while
maintaining the Deno binary distribution model.

New Files:
- package.json: npm package configuration with binary wrapper
- bin/spark-wrapper.js: Detects platform and executes correct binary
- scripts/install-binary.js: Downloads appropriate binary on npm install
- .npmignore: Excludes source files from npm package
- npmextra.json: npm extra configuration

Updated:
- readme.md: Added npm installation instructions

How It Works:
1. User runs: npm install -g @serve.zone/spark
2. Postinstall script (install-binary.js) downloads the correct
   pre-compiled binary for the user's platform from Gitea releases
3. Binary is cached in dist/binaries/
4. Wrapper script (spark-wrapper.js) executes the binary when user
   runs 'spark' command

Supported via npm:
- Linux (x64, ARM64)
- macOS (Intel, Apple Silicon)
- Windows (x64)

This maintains the benefits of Deno compilation (no runtime deps)
while providing familiar npm-based installation for users who prefer it.

.npmignore

@@ -0,0 +1,55 @@
+# Source code (not needed for binary distribution)
+/ts/
+/test/
+mod.ts
+*.ts
+!*.d.ts
+
+# Development files
+.git/
+.gitea/
+.claude/
+.serena/
+.nogit/
+.github/
+deno.json
+deno.lock
+tsconfig.json
+
+# Scripts not needed for npm
+/scripts/compile-all.sh
+install.sh
+uninstall.sh
+test.simple.ts
+
+# Documentation files not needed for npm package
+readme.plan.md
+readme.hints.md
+npm-publish-instructions.md
+docs/
+
+# IDE and editor files
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+.DS_Store
+
+# Keep only the install-binary.js in scripts/
+/scripts/*
+!/scripts/install-binary.js
+
+# Exclude all dist directory (binaries will be downloaded during install)
+/dist/
+
+# Logs and temporary files
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+
+# Other
+node_modules/
+.env
+.env.*