daily email: add intro text above form on posts

src/components/DailyEmailForm.astro

@@ -1,4 +1,5 @@
 ---
+const { intro } = Astro.props;
 ---
 
 <script src="https://f.convertkit.com/ckjs/ck.5.js"></script>
@@ -28,6 +29,8 @@
       data-stacked="false"
       class="seva-fields formkit-fields"
     >
+      {intro && (<p class="mb-8 text-center">{intro}</p>)}
+
       <div class="formkit-field">
         <input
           class="block mt-1 w-full"

src/layouts/DailyEmailLayout.astro

@@ -13,7 +13,9 @@ const { title } = Astro.props.frontmatter || Astro.props;
       <slot />
     </Markdown>
 
-    <DailyEmailForm />
+    <DailyEmailForm
+      intro='Was this useful? Sign up here and get more like this delivered straight to your inbox every day.'
+    />
 
     <AboutMe />
   </div>