feat: Add concurrency and headless options for downloads

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.

.vscode/launch.json

@@ -2,7 +2,7 @@
   "version": "0.2.0",
   "configurations": [
     {
-      "name": "download",
+      "name": "novel",
       "type": "go",
       "request": "launch",
       "mode": "auto",
@@ -10,9 +10,22 @@
       "args": [
         "download",
         "-n",
-        "2321",
-        "-v",
-        "162759"
+        "2727",
+        "--concurrency",
+        "5"
+      ]
+    },
+    {
+      "name": "volume",
+      "type": "go",
+      "request": "launch",
+      "mode": "auto",
+      "program": "${workspaceFolder}",
+      "args": [
+        "download",
+        "-n=2727",
+        "-v=150098",
+        "--headless=false"
       ]
     }
   ]