[Markdoc] `headings` and heading IDs (#7095)

* deps: markdown-remark

* wip: heading-ids function

* chore: add `@astrojs/markdoc` to external

* feat: `headings` support

* fix: allow `render` config on headings

* fix: nonexistent `userConfig`

* test: headings, toc, astro component render

* docs: README

* chore: changeset

* refactor: expose Markdoc helpers from runtime

* fix: bad named exports (commonjsssss)

* refactor: defaultNodes -> nodes

* deps: github-slugger

* fix: reset slugger cache on each render

* fix: bad astroNodes import

* docs: explain headingSlugger export

* docs: add back double stringify comment

* chore: bump to minor for internal exports change

1 files changed, 5 insertions, 1 deletions

diff --git a/packages/integrations/markdoc/src/config.ts b/packages/integrations/markdoc/src/config.ts
index 09bbead12..1a20b7431 100644
--- a/packages/integrations/markdoc/src/config.ts
+++ b/packages/integrations/markdoc/src/config.ts
@@ -1,5 +1,9 @@
 import type { ConfigType as MarkdocConfig } from '@markdoc/markdoc';
-export { default as Markdoc } from '@markdoc/markdoc';
+import { nodes as astroNodes } from './nodes/index.js';
+import _Markdoc from '@markdoc/markdoc';
+
+export const Markdoc = _Markdoc;
+export const nodes = { ...Markdoc.nodes, ...astroNodes };
 
 export function defineMarkdocConfig(config: MarkdocConfig): MarkdocConfig {
 	return config;