Add set-version task to set version from package.json

tasks/set-version.js

@@ -0,0 +1,23 @@
+const fs = require('fs');
+const pkg = require('../package.json');
+
+const index = require.resolve('../src/ol/index');
+const lines = fs.readFileSync(index, 'utf-8').split('\n');
+
+const versionRegEx = /const VERSION = '(.*)';$/;
+
+for (let i = 0, ii = lines.length; i < ii; ++i) {
+  const line = lines[i];
+  if (versionRegEx.test(line)) {
+    lines[i] = line.replace(versionRegEx, `const VERSION = '${pkg.version}';`);
+    break;
+  }
+}
+
+const packageJson = require.resolve('../src/ol/package.json');
+const packageJsonObj = JSON.parse(fs.readFileSync(packageJson, 'utf-8'));
+packageJsonObj.version = pkg.version;
+fs.writeFileSync(packageJson, JSON.stringify(packageJsonObj, null, 2), 'utf-8');
+
+
+fs.writeFileSync(index, lines.join('\n'), 'utf-8');