Add sheet music page, some slight changes

src/components/MDX/H1.astro

@@ -1 +1,5 @@
-<h1 class="font-header text-3xl"><slot /></h1>
+---
+const { class: className, ...attrs } = Astro.props;
+---
+
+<h1 class:list={["font-header text-3xl", className]} {...attrs}><slot /></h1>

src/components/MDX/H2.astro

@@ -1 +1,5 @@
-<h2 class="font-header text-2xl"><slot /></h2>
+---
+const { class: className, ...attrs } = Astro.props;
+---
+
+<h2 class:list={["font-header text-2xl", className]} {...attrs}><slot /></h2>

src/components/MDX/LI.astro

@@ -1,2 +1,5 @@
-<span class="block p-0.5"><span class="text-primary pr-2">•</span><slot /></span
->
+<li>
+  <span class="block p-0.5"
+    ><span class="text-primary pr-2">•</span><slot /></span
+  >
+</li>