Initial commit: Manga Mass Downloader Chrome Extension

✨ Features:
- Multi-selection checkboxes on manga listings
- Batch download selected manga or all manga from page
- Optimized parallel downloading (20ms delays, 5 concurrent)
- Visual progress tracking
- Popup UI for easy control
- Fixed duplicate checkbox issue with deduplication logic

📁 Files:
- manifest.json: Extension configuration
- content.js: Checkbox injection & manga detection
- background.js: Optimized download engine
- popup.html/js: User interface
- README.md: Complete documentation

manifest.json

@@ -0,0 +1,39 @@
+{
+  "manifest_version": 3,
+  "name": "Manga Mass Downloader",
+  "version": "1.0.0",
+  "description": "Descarga múltiples manga desde listados de e-hentai.org",
+  "permissions": [
+    "activeTab",
+    "storage",
+    "downloads"
+  ],
+  "host_permissions": [
+    "https://e-hentai.org/*",
+    "https://exhentai.org/*",
+    "https://*.hath.network/*"
+  ],
+  "content_scripts": [
+    {
+      "matches": [
+        "https://e-hentai.org/*",
+        "https://exhentai.org/*"
+      ],
+      "js": ["content.js"],
+      "run_at": "document_end"
+    }
+  ],
+  "background": {
+    "service_worker": "background.js"
+  },
+  "action": {
+    "default_popup": "popup.html",
+    "default_title": "Manga Mass Downloader"
+  },
+  "web_accessible_resources": [
+    {
+      "resources": ["*.js", "*.css"],
+      "matches": ["<all_urls>"]
+    }
+  ]
+}