extract tidy-tree layout into separate package

on-behalf-of: @Mermaid-Chart <hello@mermaidchart.com>

packages/mermaid-layout-tidy-tree/README.md

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+# @mermaid-js/layout-tidy-tree
+
+This package provides a bidirectional tidy tree layout engine for Mermaid based on the non-layered-tidy-tree-layout algorithm.
+
+> [!NOTE]
+> The Tidy Tree Layout engine will not be available in all providers that support mermaid by default.
+> The websites will have to install the @mermaid-js/layout-tidy-tree package to use the Tidy Tree layout engine.
+
+## Usage
+
+flowchart-tidy-tree TD
+A --> B
+A --> C
+
+---
+
+config:
+layout: tidy-tree
+
+---
+
+flowchart TD
+A --> B
+A --> C
+
+### With bundlers
+
+sh
+npm install @mermaid-js/layout-tidy-tree
+
+ts
+import mermaid from 'mermaid';
+import tidyTreeLayouts from '@mermaid-js/layout-tidy-tree';
+
+mermaid.registerLayoutLoaders(tidyTreeLayouts);
+
+### With CDN
+
+html
+
+<script type="module">
+  import mermaid from 'https://cdn.jsdelivr.net/npm/mermaid@11/dist/mermaid.esm.min.mjs';
+  import tidyTreeLayouts from 'https://cdn.jsdelivr.net/npm/@mermaid-js/layout-tidy-tree@0/dist/mermaid-layout-tidy-tree.esm.min.mjs';
+
+  mermaid.registerLayoutLoaders(tidyTreeLayouts);
+</script>
+
+## Supported layouts
+
+tidy-tree: The bidirectional tidy tree layout
+
+The bidirectional tidy tree layout algorithm creates two separate trees that grow horizontally in opposite directions from a central root node:
+Left tree: grows horizontally to the left (children alternate: 1st, 3rd, 5th...)
+Right tree: grows horizontally to the right (children alternate: 2nd, 4th, 6th...)
+
+This creates a balanced, symmetric layout that is ideal for mindmaps, organizational charts, and other tree-based diagrams.
+
+Layout Structure:
+[Child 3] ← [Child 1] ← [Root] → [Child 2] → [Child 4]
+↓ ↓ ↓ ↓
+[GrandChild] [GrandChild] [GrandChild] [GrandChild]