Upgrade unified deps and improve unified plugins types (#1200)

* Upgrade @astrojs/markdown-support deps and update types

* Add changeset

* Update changeset

* Switch astro-markdown-plugins example to use rehype-autolink-headings

Usage of remark-autolink-headings is discouraged in favor of the rehype counterpart: https://github.com/remarkjs/remark-autolink-headings\#remark-autolink-headings

* Add stricter types for unified plugins

This includes a few suggestions from a code review:
- use vfile.toString instead of vfile.value.toString
- refactor plugins to follow unified best practices instead of returning functions that return a plugin
- use any instead of any[] for plugin options types

* Narrow down types to more specific hast or mdast typings

1 files changed, 2 insertions, 1 deletions

diff --git a/examples/with-markdown-plugins/astro.config.mjs b/examples/with-markdown-plugins/astro.config.mjs
index 690d8f434..fa9d48a1b 100644
--- a/examples/with-markdown-plugins/astro.config.mjs
+++ b/examples/with-markdown-plugins/astro.config.mjs
@@ -10,8 +10,9 @@
 export default /** @type {import('astro').AstroUserConfig} */ ({
   // Enable Custom Markdown options, plugins, etc.
   markdownOptions: {
-    remarkPlugins: ['remark-code-titles', 'remark-slug', ['remark-autolink-headings', { behavior: 'prepend' }]],
+    remarkPlugins: ['remark-code-titles', 'remark-slug'],
     rehypePlugins: [
+      ['rehype-autolink-headings', { behavior: 'prepend' }],
       ['rehype-toc', { headings: ['h2', 'h3'] }],
       ['rehype-add-classes', { 'h1,h2,h3': 'title' }],
     ],