feat(cli): add command line interface with comprehensive features

Implements a full-featured CLI for Crawl4AI with the following capabilities:
- Basic and advanced web crawling
- Configuration management via YAML/JSON files
- Multiple extraction strategies (CSS, XPath, LLM)
- Content filtering and optimization
- Interactive Q&A capabilities
- Various output formats
- Comprehensive documentation and examples

Also includes:
- Home directory setup for configuration and cache
- Environment variable support for API tokens
- Test suite for CLI functionality

tests/cli/test_cli.py

@@ -0,0 +1,133 @@
+import pytest
+from click.testing import CliRunner
+from pathlib import Path
+import json
+import yaml
+from crawl4ai.cli import cli, load_config_file, parse_key_values
+import tempfile
+import os
+import click
+
+@pytest.fixture
+def runner():
+    return CliRunner()
+
+@pytest.fixture
+def temp_config_dir():
+    with tempfile.TemporaryDirectory() as tmpdir:
+        old_home = os.environ.get('HOME')
+        os.environ['HOME'] = tmpdir
+        yield Path(tmpdir)
+        if old_home:
+            os.environ['HOME'] = old_home
+
+@pytest.fixture
+def sample_configs(temp_config_dir):
+    configs = {
+        'browser.yml': {
+            'headless': True,
+            'viewport_width': 1280,
+            'user_agent_mode': 'random'
+        },
+        'crawler.yml': {
+            'cache_mode': 'bypass',
+            'wait_until': 'networkidle',
+            'scan_full_page': True
+        },
+        'extract_css.yml': {
+            'type': 'json-css',
+            'params': {'verbose': True}
+        },
+        'css_schema.json': {
+            'name': 'ArticleExtractor',
+            'baseSelector': '.article',
+            'fields': [
+                {'name': 'title', 'selector': 'h1.title', 'type': 'text'},
+                {'name': 'link', 'selector': 'a.read-more', 'type': 'attribute', 'attribute': 'href'}
+            ]
+        }
+    }
+    
+    for filename, content in configs.items():
+        path = temp_config_dir / filename
+        with open(path, 'w') as f:
+            if filename.endswith('.yml'):
+                yaml.dump(content, f)
+            else:
+                json.dump(content, f)
+                
+    return {name: str(temp_config_dir / name) for name in configs}
+
+class TestCLIBasics:
+    def test_help(self, runner):
+        result = runner.invoke(cli, ['--help'])
+        assert result.exit_code == 0
+        assert 'Crawl4AI CLI' in result.output
+
+    def test_examples(self, runner):
+        result = runner.invoke(cli, ['--example'])
+        assert result.exit_code == 0
+        assert 'Examples' in result.output
+
+    def test_missing_url(self, runner):
+        result = runner.invoke(cli)
+        assert result.exit_code != 0
+        assert 'URL argument is required' in result.output
+
+class TestConfigParsing:
+    def test_parse_key_values_basic(self):
+        result = parse_key_values(None, None, "key1=value1,key2=true")
+        assert result == {'key1': 'value1', 'key2': True}
+
+    def test_parse_key_values_invalid(self):
+        with pytest.raises(click.BadParameter):
+            parse_key_values(None, None, "invalid_format")
+
+class TestConfigLoading:
+    def test_load_yaml_config(self, sample_configs):
+        config = load_config_file(sample_configs['browser.yml'])
+        assert config['headless'] is True
+        assert config['viewport_width'] == 1280
+
+    def test_load_json_config(self, sample_configs):
+        config = load_config_file(sample_configs['css_schema.json'])
+        assert config['name'] == 'ArticleExtractor'
+        assert len(config['fields']) == 2
+
+    def test_load_nonexistent_config(self):
+        with pytest.raises(click.BadParameter):
+            load_config_file('nonexistent.yml')
+
+class TestLLMConfig:
+    def test_llm_config_creation(self, temp_config_dir, runner):
+        def input_simulation(inputs):
+            return runner.invoke(cli, ['https://example.com', '-q', 'test question'], 
+                               input='\n'.join(inputs))
+            
+class TestCrawlingFeatures:
+    def test_basic_crawl(self, runner):
+        result = runner.invoke(cli, ['https://example.com'])
+        assert result.exit_code == 0
+
+
+class TestErrorHandling:
+    def test_invalid_config_file(self, runner):
+        result = runner.invoke(cli, [
+            'https://example.com',
+            '--browser-config', 'nonexistent.yml'
+        ])
+        assert result.exit_code != 0
+
+    def test_invalid_schema(self, runner, temp_config_dir):
+        invalid_schema = temp_config_dir / 'invalid_schema.json'
+        with open(invalid_schema, 'w') as f:
+            f.write('invalid json')
+            
+        result = runner.invoke(cli, [
+            'https://example.com',
+            '--schema', str(invalid_schema)
+        ])
+        assert result.exit_code != 0
+
+if __name__ == '__main__':
+    pytest.main(['-v', '-s', '--tb=native', __file__])