fix: update platform support docs for cross-runtime compatibility

- README: Node.js 18+ → Node.js 18+, Deno, and Bun
- package.json: add deno:true field
- build-distribution.md: consolidate engine/platform sections

package.json

@@ -146,5 +146,6 @@
   },
   "engines": {
     "node": ">=18.0.0"
-  }
-}
+  },
+  "deno": true
+}