feat(cli): add quick JSON extraction and global config management

Adds new features to improve user experience and configuration:
- Quick JSON extraction with -j flag for direct LLM-based structured data extraction
- Global configuration management with 'crwl config' commands
- Enhanced LLM extraction with better JSON handling and error management
- New user settings for default behaviors (LLM provider, browser settings, etc.)

Breaking changes: None

crawl4ai/config.py

@@ -93,3 +93,46 @@ SHOW_DEPRECATION_WARNINGS = True
 SCREENSHOT_HEIGHT_TRESHOLD = 10000
 PAGE_TIMEOUT = 60000
 DOWNLOAD_PAGE_TIMEOUT = 60000
+
+# Global user settings with descriptions and default values
+USER_SETTINGS = {
+    "DEFAULT_LLM_PROVIDER": {
+        "default": "openai/gpt-4o",
+        "description": "Default LLM provider in 'company/model' format (e.g., 'openai/gpt-4o', 'anthropic/claude-3-sonnet')",
+        "type": "string"
+    },
+    "DEFAULT_LLM_PROVIDER_TOKEN": {
+        "default": "",
+        "description": "API token for the default LLM provider",
+        "type": "string",
+        "secret": True
+    },
+    "VERBOSE": {
+        "default": False,
+        "description": "Enable verbose output for all commands",
+        "type": "boolean"
+    },
+    "BROWSER_HEADLESS": {
+        "default": True,
+        "description": "Run browser in headless mode by default",
+        "type": "boolean"
+    },
+    "BROWSER_TYPE": {
+        "default": "chromium",
+        "description": "Default browser type (chromium or firefox)",
+        "type": "string",
+        "options": ["chromium", "firefox"]
+    },
+    "CACHE_MODE": {
+        "default": "bypass",
+        "description": "Default cache mode (bypass, use, or refresh)",
+        "type": "string",
+        "options": ["bypass", "use", "refresh"]
+    },
+    "USER_AGENT_MODE": {
+        "default": "default",
+        "description": "Default user agent mode (default, random, or mobile)",
+        "type": "string",
+        "options": ["default", "random", "mobile"]
+    }
+}