fix(markdown): include content of all tokens in heading ids

closes #4561

BREAKING CHANGES: The heading ids might change in some cases if you're using special (non-html) elements in headings. Please update the broken links to fragments if you find any. To revert back to the older behavior you can customize `markdown.anchor.getTokensText`.

src/node/markdown/markdown.ts

@@ -263,6 +263,12 @@ export async function createMarkdownRenderer(
   // mdit-vue plugins
   md.use(anchorPlugin, {
     slugify,
+    getTokensText: (tokens) => {
+      return tokens
+        .filter((token) => token.type !== 'html_inline')
+        .map((token) => token.content)
+        .join('')
+    },
     permalink: anchorPlugin.permalink.linkInsideHeader({
       symbol: '​',
       renderAttrs: (slug, state) => {