extract tidy-tree layout into separate package

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

packages/mermaid-layout-tidy-tree/src/layouts.ts

@@ -0,0 +1,13 @@
+import type { LayoutLoaderDefinition } from 'mermaid';
+
+const loader = async () => await import(`./render.js`);
+
+const layouts: LayoutLoaderDefinition[] = [
+  {
+    name: 'tidy-tree',
+    loader,
+    algorithm: 'tidy-tree',
+  },
+];
+
+export default layouts;