support for stripping off frontmatter

src/frontmatter.ts

@@ -0,0 +1,18 @@
+
+import * as yaml from 'yaml';
+
+export function process_frontmatter(document: string) {
+	if (! document.startsWith('---\n')) {
+		return {
+			frontmatter: null,
+			markdown: document,
+		};
+	}
+
+	const endIndex = document.slice(3).indexOf('\n---\n') + 3;
+	const frontmatterYaml = document.slice(3, endIndex);
+	const markdown = document.slice(endIndex + 4);
+	const frontmatter = yaml.parse(frontmatterYaml);
+
+	return { frontmatter, markdown };
+}