Remove artifacts and set language of markdown sites

.gitattributes

@@ -0,0 +1,2 @@
+*.md linguist-language=Astro
+*.mdx linguist-language=Astro

src/remark-modified-time.mjs

@@ -1,22 +0,0 @@
-import { execSync } from "child_process";
-import { statSync } from "fs";
-
-export function remarkModifiedTime() {
-  return function (tree, file) {
-    const filepath = file.history[0];
-    try {
-        const result = execSync(`git log -1 --pretty="format:%cI" "${filepath}"`);
-        // If  result is empty or undefined, fallback to fs stat
-        if (!result || !result.toString().trim()) {
-            throw new Error("No git history");
-        } 
-        file.data.astro.frontmatter.lastModified = result.toString();
-        return;
-    } catch (e) {
-        // Ignore, fallback to fs stat
-        const result = statSync(filepath);
-        file.data.astro.frontmatter.lastModified = result.mtime.toISOString();
-        return;
-    }
-  };
-}