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/04-multi-step-form.c4a

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+# Multi-step Form Wizard
+# Complete a complex form with multiple steps
+
+# Navigate to forms section
+CLICK `a[href="#forms"]`
+WAIT `#survey-form` 2
+
+# Step 1: Basic Information
+CLICK `#full-name`
+TYPE "John Doe"
+
+CLICK `#survey-email`  
+TYPE "john.doe@example.com"
+
+# Go to next step
+CLICK `.next-step`
+WAIT 1
+
+# Step 2: Select Interests
+# Select multiple options
+CLICK `#interests`
+CLICK `option[value="tech"]`
+CLICK `option[value="music"]`
+CLICK `option[value="travel"]`
+
+# Continue to final step
+CLICK `.next-step`
+WAIT 1
+
+# Step 3: Review and Submit
+# Verify we're on the last step
+IF (EXISTS `#submit-survey`) THEN EVAL `console.log('📋 On final step')`
+
+# Submit the form
+CLICK `#submit-survey`
+
+# Wait for success message
+WAIT `.success-message` 5
+
+# Verify submission
+IF (EXISTS `.success-message`) THEN EVAL `console.log('✅ Survey submitted successfully!')`