v2.0.0

• Support zero-prefixed style: 00:00 Chapter Title. Thanks @Kacper-Lubisz!
• Support bracketed styles: [0:00] Chapter Title / (0:00) Chapter Title. Thanks @unreleased!
• Remove extended: true option. YouTube now supports the formats that the option enabled,
  so the library has also accepts those formats by default.
• The library now uses some ES6 syntax like const. If you are targeting pre-modern browsers,
  you may need to configure a transpiler.