test: add plugins

src/plugins/remark-excerpt.ts

@@ -0,0 +1,26 @@
+import type { Root } from 'mdast'
+import { toString } from 'mdast-util-to-string'
+
+interface AstroData {
+  data: {
+    astro: {
+      frontmatter: {
+        excerpt: string
+      }
+    }
+  }
+}
+
+export function remarkExcerpt() {
+  return (tree: Root, file: AstroData) => {
+    let excerpt = ''
+    for (const node of tree.children) {
+      if (node.type !== 'paragraph') {
+        continue
+      }
+      excerpt = toString(node)
+      break
+    }
+    file.data.astro.frontmatter.excerpt = excerpt
+  }
+}