Updated the build system

gulpfile.esm.js

@@ -28,7 +28,7 @@ task('coverage', () => _exec('coveralls', ['var/lcov.info']));
 /** Builds the documentation. */
 task('doc', async () => {
   for (const path of ['CHANGELOG.md', 'LICENSE.md']) await copyFile(path, `doc/about/${path.toLowerCase()}`);
-  await _exec('esdoc', ['-c', 'etc/esdoc.json']);
+  await _exec('jsdoc', ['--configure', 'etc/jsdoc.json']);
   await _exec('mkdocs', ['build', '--config-file=etc/mkdocs.yaml']);
   return del(['doc/about/changelog.md', 'doc/about/license.md']);
 });
@@ -50,7 +50,7 @@ task('upgrade', async () => {
   await _exec('git', ['reset', '--hard']);
   await _exec('git', ['fetch', '--all', '--prune']);
   await _exec('git', ['pull', '--rebase']);
-  await _exec('npm', ['install', '--ignore-scripts']));
+  await _exec('npm', ['install', '--ignore-scripts']);
   return _exec('npm', ['update', '--dev']);
 });
 
@@ -65,7 +65,7 @@ task('default', task('test'));
  * @param {string} command The command to run.
  * @param {string[]} [args] The command arguments.
  * @param {SpawnOptions} [options] The settings to customize how the process is spawned.
- * @return {Promise<void>} Completes when the command is finally terminated.
+ * @return {Promise} Completes when the command is finally terminated.
  */
 function _exec(command, args = [], options = {}) {
   return new Promise((fulfill, reject) => spawn(normalize(command), args, {shell: true, stdio: 'inherit', ...options})