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.

readme.md

@@ -25,6 +25,14 @@ Install the latest version via our installation script:
 curl -sSL https://code.foss.global/serve.zone/spark/raw/branch/master/install.sh | sudo bash
 ```
 
+### npm Install
+
+Install via npm (automatically downloads the correct binary for your platform):
+
+```bash
+npm install -g @serve.zone/spark
+```
+
 ### Specific Version
 
 ```bash