Add support for use singe pic on post

templates/editor.html

@@ -2,11 +2,12 @@
 {% block title %}{{ 'Edit' if post else 'Write' }} | Eternity Project{% endblock %}
 {% block content %}
 <section class="editor-wrap"><div class="section-head"><span>{{ 'EDIT TRANSMISSION' if post else 'NEW TRANSMISSION' }}</span><span>AUTHOR / {{ current_user.username }}</span></div>
-<form class="editor-form" method="post">
+<form class="editor-form" method="post" enctype="multipart/form-data">
   <input type="hidden" name="csrf_token" value="{{ csrf_token() }}">
   <label>Title<input name="title" required value="{{ post.title if post else '' }}" placeholder="A clear, useful heading"></label>
   <div class="two-col"><label>Category<input name="category" value="{{ post.category if post else 'Engineering' }}" placeholder="Engineering"></label><label>Summary<input name="excerpt" required value="{{ post.excerpt if post else '' }}" placeholder="The one-paragraph signal"></label></div>
   <label>Article<textarea name="body" required rows="16" placeholder="Write in plain text. Paragraph breaks are preserved.">{{ post.body if post else '' }}</textarea></label>
+  <label>Article image<input name="image" type="file" accept="image/jpeg,image/png,image/webp">{% if post and post.image_filename %}<small>Leave empty to retain the current image.</small>{% endif %}</label>
   <button class="button" type="submit">Publish transmission <span aria-hidden="true">→</span></button>
 </form>
 </section>