feat: render markdown content using marked library

EnvelopeGenerator.Web/Views/Envelope/ShowEnvelope.cshtml

@@ -79,7 +79,7 @@
                 }
                 else
                 {
-                <div id="envelope-message"></div>
+                <div class="markdown">@(envelope?.Message)</div>
                 }
                 <p>
                     <small class="text-body-secondary">
@@ -134,8 +134,6 @@
 @if (!isReadOnly)
 {
 <script nonce="@nonce">
-    document.getElementById('envelope-message').innerHTML = marked.parse('@(envelope?.Message)');
-
     document.getElementById('readonly-send').addEventListener('click', async () => {
         const receiverMail = document.getElementById('readonly-receiver-mail');
         const dateValid = document.getElementById('readonly-date-valid');