Expose version property in public API

This value is already used in the conversion tooling and is useful
in external contexts too, for example when specifying/detecting
node-addon-api as an optional peer dependency.

Also adds test expectations for all exported properties.

index.js

@@ -1,4 +1,5 @@
 const path = require('path');
+const { version } = require('./package.json');
 
 const includeDir = path.relative('.', __dirname);
 
@@ -7,6 +8,7 @@ module.exports = {
   include_dir: includeDir,
   gyp: path.join(includeDir, 'node_api.gyp:nothing'), // deprecated.
   targets: path.join(includeDir, 'node_addon_api.gyp'),
+  version,
   isNodeApiBuiltin: true,
   needsFlag: false
 };

package.json

@@ -431,7 +431,8 @@
     "fs-extra": "^11.1.1",
     "path": "^0.12.7",
     "pre-commit": "^1.2.2",
-    "safe-buffer": "^5.1.1"
+    "safe-buffer": "^5.1.1",
+    "semver": "^7.6.0"
   },
   "directories": {},
   "gypfile": false,

test/exports.js

@@ -0,0 +1,18 @@
+'use strict';
+
+const { strictEqual } = require('assert');
+const { valid } = require('semver');
+
+const nodeAddonApi = require('../');
+
+module.exports = function test () {
+  strictEqual(nodeAddonApi.include.startsWith('"'), true);
+  strictEqual(nodeAddonApi.include.endsWith('"'), true);
+  strictEqual(nodeAddonApi.include.includes('node-addon-api'), true);
+  strictEqual(nodeAddonApi.include_dir, '');
+  strictEqual(nodeAddonApi.gyp, 'node_api.gyp:nothing');
+  strictEqual(nodeAddonApi.targets, 'node_addon_api.gyp');
+  strictEqual(valid(nodeAddonApi.version), true);
+  strictEqual(nodeAddonApi.isNodeApiBuiltin, true);
+  strictEqual(nodeAddonApi.needsFlag, false);
+};

tools/conversion.js

@@ -12,7 +12,7 @@ if (!dir) {
   process.exit(1);
 }
 
-const NodeApiVersion = require('../package.json').version;
+const NodeApiVersion = require('../').version;
 
 const disable = args[1];
 let ConfigFileOperations;