This commit introduces new features for controlling the download process:
- **Concurrency**: Users can now specify the number of concurrent volume downloads using the `--concurrency` flag. This significantly speeds up the download of entire novels.
- **Headless Mode**: A `--headless` flag has been added to control whether the browser operates in headless mode (without a visible UI). This is useful for debugging or running in environments without a display.
**Changes include:**
- Updated `download` command to accept `--concurrency` and `--headless` flags.
- Refactored `bilinovel` downloader to support `BilinovelNewOption` for configuring headless mode and concurrency.
- Implemented a page pool and concurrency control mechanism within the `bilinovel` downloader to manage concurrent browser page usage.
- Added `DownloadNovel` and `DownloadVolume` methods to the `bilinovel` downloader, utilizing goroutines and wait groups for parallel processing.
- Updated `.vscode/launch.json` with new configurations for testing novel and volume downloads with the new options.
