Fix: bun runtime silently returns empty object for NAPI (#28)

bindings.js

@@ -1 +1,11 @@
-module.exports = require('./lib/api')(require('node-gyp-build')(__dirname))
+const nativeAddon = require('node-gyp-build')(__dirname)
+if (typeof nativeAddon !== 'function') {
+  // Some new runtimes (bun) don't support N-API
+  // but the build step incorrectly succeeds.
+  // The value should be a function, but in bun it returns
+  // an empty object {} so we use typeof to check that
+  // it is a function and throw otherwise.
+  // This throw will cause "keccak" import to fallback to JS.
+  throw new Error('Native add-on failed to load')
+}
+module.exports = require('./lib/api')(nativeAddon)