ESM build of `decap-cms-widget-richtext` includes invalid imports

**Describe the bug**
When using `decap-cms-app` in an Astro/Vite app, there are issues due incorrect import statements in the `decap-cms-widget-richtext`.

For example I get:

```
✘ [ERROR] No matching export in "node_modules/.pnpm/unist-util-visit-parents@6.0.2/node_modules/unist-util-visit-parents/index.js" for import "default"

node_modules/.pnpm/decap-cms-widget-richtext@3.2.1_@emotion+react@11.14.0_@types+react@19.2.14_react@19.2.5__@em_hhy545oktf22w3cpgrsx7kwr6i/node_modules/decap-cms-widget-richtext/dist/esm/serializers/remarkAssertParents.js:2:7:
2 │ import visitParents from 'unist-util-visit-parents';
╵ ~~~~~~~~~~~~
```

`visitParents` is [a named export of `unist-util-visit-parents`](https://npmx.dev/package-code/unist-util-visit-parents/v/6.0.2/index.js#L2), not a default export so the resolution fails here:

https://github.com/decaporg/decap-cms/blob/6ef2f9bdf81ce9df55642fe1414e5e687cff95fd/packages/decap-cms-widget-richtext/src/serializers/remarkAssertParents.js#L2

The same issue is present for the import of `mdastDefinitions` here:

https://github.com/decaporg/decap-cms/blob/6ef2f9bdf81ce9df55642fe1414e5e687cff95fd/packages/decap-cms-widget-richtext/src/serializers/remarkSquashReferences.js#L3

**Expected behavior**

The imports should be correct

**Applicable Versions:**

- Decap CMS version: `"decap-cms-app": "^3.12.2"`
- OS: macOS
- Browser version: Firefox 150
- Node.JS version: 24.15

**CMS configuration**
This happens with any config, even when not using the rich text widget