Enable frontmatter extension of the parser

src/main.rs

@@ -7,10 +7,20 @@ use clap::Parser;
 use md_to_html::{file, html, parser};
 use std::path::Path;
 use std::process::exit;
+use markdown::{Options, Constructs, ParseOptions, CompileOptions};
 
 fn main() {
     let args = Cli::parse();
-    let parser = parser::Parser::new(markdown::Options::gfm());
+    let parser = parser::Parser::new(Options{
+      parse: ParseOptions {
+        constructs: Constructs {
+            frontmatter: true,
+            ..Constructs::default()
+        },
+        ..ParseOptions::default()
+      },
+      compile: CompileOptions::gfm()
+    });
     let html = html::Html::new();
 
     match args.command {