feat(demarche): describe procedure prefilling (#8187)

* feat(demarche): description

Show the description of an opendata procedure (published or draft),
with help about how to prefill a dossier for this procedure.

Co-authored-by: Damien Le Thiec <damien.lethiec@gmail.com>

app/assets/stylesheets/confirmations.scss

@@ -37,6 +37,7 @@
   }
 
   .confirmation-resend {
+
     p,
     label {
       margin-bottom: $default-padding;