Create "Apps" section in documentation and Add interactive c4a-script playground and LLM context builder for Crawl4AI

- Created a new HTML page (`index.html`) for the interactive LLM context builder, allowing users to select and combine different `crawl4ai` context files.
- Implemented JavaScript functionality (`llmtxt.js`) to manage component selection, context types, and file downloads.
- Added CSS styles (`llmtxt.css`) for a terminal-themed UI.
- Introduced a new Markdown file (`build.md`) detailing the requirements and functionality of the context builder.
- Updated the navigation in `mkdocs.yml` to include links to the new context builder and demo apps.
- Added a new Markdown file (`why.md`) explaining the motivation behind the new context structure and its benefits for AI coding assistants.

docs/md_v2/apps/c4a-script/scripts/03-infinite-scroll.c4a

@@ -0,0 +1,32 @@
+# Infinite Scroll Product Loading
+# Load all products using scroll automation
+
+# Navigate to catalog
+CLICK `#catalog-link`
+WAIT `.product-grid` 3
+
+# Switch to infinite scroll mode
+CLICK `#infinite-scroll-btn`
+
+# Define scroll procedure
+PROC load_more_products
+  # Get current product count
+  EVAL `window.initialCount = document.querySelectorAll('.product-card').length`
+  
+  # Scroll down
+  SCROLL DOWN 1000
+  WAIT 2
+  
+  # Check if more products loaded
+  EVAL `
+    const newCount = document.querySelectorAll('.product-card').length;
+    console.log('Products loaded: ' + newCount);
+    window.moreLoaded = newCount > window.initialCount;
+  `
+ENDPROC
+
+# Load products until no more
+REPEAT (load_more_products, `window.moreLoaded !== false`)
+
+# Final count
+EVAL `console.log('✅ Total products: ' + document.querySelectorAll('.product-card').length)`