Ensure frontmatter regex matches first possible closing delimiter

src/main.rs

@@ -168,7 +168,7 @@ fn main() {
             },
         };
 
-        let fm_re = RegexBuilder::new(r"---\n(?<frontmatter>.+)\n---")
+        let fm_re = RegexBuilder::new(r"---\n(?<frontmatter>([^-]*?))\n---")
             .dot_matches_new_line(true)
             .build()
             .unwrap();