feat(rehype-docz): add mdx exports to Playground scope

#1247

core/rehype-docz/src/index.ts

@@ -3,6 +3,7 @@ import nodeToString from 'hast-util-to-string'
 import { format } from 'docz-utils/lib/format'
 import { componentName, sanitizeCode, removeTags } from 'docz-utils/lib/jsx'
 import { getImportsVariables } from 'docz-utils/lib/imports'
+import { getExportsVariables } from 'docz-utils/lib/exports'
 
 const isPlayground = (name: string) => {
   return name === 'Playground'
@@ -34,7 +35,13 @@ export interface PluginOpts {
 
 export default () => (tree: any) => {
   const importNodes = tree.children.filter((n: any) => n.type === 'import')
-  const scopes: string[] = flatten(importNodes.map(getImportsVariables))
+  const exportNodes = tree.children.filter((n: any) => n.type === 'export')
+  const importedScopes = flatten<string>(importNodes.map(getImportsVariables))
+  const exportedScopes = flatten<string>(exportNodes.map(getExportsVariables))
+  // filter added to avoid throwing if an unexpected type is exported
+  const scopes: string[] = [...importedScopes, ...exportedScopes].filter(
+    Boolean
+  )
   const nodes = tree.children
     .filter((node: any) => node.type === 'jsx')
     .map(addComponentsProps(scopes))