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

docs/examples/cli/css_schema.json

@@ -0,0 +1,27 @@
+{
+  "name": "ArticleExtractor",
+  "baseSelector": ".cards[data-tax=news] .card__data",
+  "fields": [
+    {
+      "name": "title",
+      "selector": "h4.card__title",
+      "type": "text"
+    },
+    {
+      "name": "link",
+      "selector": "h4.card__title a", 
+      "type": "attribute",
+      "attribute": "href"
+    },
+    {
+      "name": "details",
+      "selector": ".card__details",
+      "type": "text"
+    },
+    {
+      "name": "topics",
+      "selector": ".card__topics.topics",
+      "type": "text"
+    }
+  ]
+}