How to use the mermaid elk layout?

[tekumara]

I'd like this to use the elk layout:

```mermaid { layout: 'elk' }

graph TD
    A[history=None]
    B[history='b']

    A --->|Set| B
    B --->|Set| B
```

[tekumara]

1. First run: npm install @mermaid-js/layout-elk

2. Then add the following to setup/main.ts:

   import { defineAppSetup } from '@slidev/types';
   import mermaid from 'mermaid/dist/mermaid.esm.mjs';
   import elkLayouts from '@mermaid-js/layout-elk';
   
   mermaid.registerLayoutLoaders(elkLayouts);
   
   export default defineAppSetup(() => {})

See https://www.npmjs.com/package/@mermaid-js/layout-elk