Render feed from episode (#9)

- Render chapter if present (#5)
- Render transcript if present (#8)
- Require transcript type if URL entered (#8)

src/admin-theme/wwwroot/admin.js

@@ -255,6 +255,13 @@
     document.getElementById(`link_${idx}`).remove()
   },
 
+  /**
+   * Require transcript type if transcript URL is present
+   */
+  requireTranscriptType() {
+    document.getElementById("transcriptType").required = document.getElementById("transcriptUrl").value.trim() !== ""
+  },
+
   /**
    * Show messages that may have come with an htmx response
    * @param messages The messages from the response