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/01-basic-interaction.c4a

@@ -0,0 +1,18 @@
+# Basic Page Interaction
+# This script demonstrates basic C4A commands
+
+# Navigate to the playground
+GO http://127.0.0.1:8080/playground/
+
+# Wait for page to load
+WAIT `body` 2
+
+# Handle cookie banner if present
+IF (EXISTS `.cookie-banner`) THEN CLICK `.accept`
+
+# Close newsletter popup if it appears
+WAIT 3
+IF (EXISTS `.newsletter-popup`) THEN CLICK `.close`
+
+# Click the start tutorial button
+CLICK `#start-tutorial`