widgets: Unify spacing beneath widgets and spoilers.

web/styles/rendered_markdown.css

@@ -235,10 +235,9 @@
         border: hsl(0deg 0% 50%) 1px solid;
         padding: 2px 8px 2px 10px;
         border-radius: 10px;
-        position: relative;
-        top: 1px;
-        display: block;
-        margin: 5px 0 15px;
+        /* Space any subsequent Markdown content the same
+           distance as adjacent paragraphs are spaced. */
+        margin: 0 0 10px;
 
         .spoiler-header {
             /* We use flexbox to display the spoiler message
@@ -332,6 +331,13 @@
         }
     }
 
+    & > .spoiler-block:last-child {
+        /* A spoiler block at the end of a message, or as
+           a message's only content, gets the same bottom
+           margin as other elements. */
+        margin-bottom: 5px;
+    }
+
     /* embedded link previews */
     .message_inline_image_title {
         font-weight: bold;

web/styles/widgets.css

@@ -1,3 +1,9 @@
+.widget-content {
+    /* TODO: Coordinate this value with other Markdown
+       element spacing, as a variable. */
+    margin-bottom: 5px;
+}
+
 .widget-choices {
     & ul {
         padding: 3px;
@@ -67,10 +73,6 @@
             }
         }
     }
-
-    .add-task-bar {
-        margin-bottom: 5px;
-    }
 }
 
 .todo-widget,

web/templates/widgets/poll_widget.hbs

@@ -18,5 +18,4 @@
         <input type="text" class="poll-option" placeholder="{{t 'New option'}}" />
         <button class="poll-option">{{t "Add option" }}</button>
     </div>
-    <br />
 </div>