add: unit and integration testing

app/node_modules/node-addon-api/index.js

@@ -0,0 +1,12 @@
+const path = require('path');
+
+const includeDir = path.relative('.', __dirname);
+
+module.exports = {
+  include: `"${__dirname}"`, // deprecated, can be removed as part of 4.0.0
+  include_dir: includeDir,
+  gyp: path.join(includeDir, 'node_api.gyp:nothing'), // deprecated.
+  targets: path.join(includeDir, 'node_addon_api.gyp'),
+  isNodeApiBuiltin: true,
+  needsFlag: false
+};