use monospace styling for documentation text

packages/completer/src/widget.ts

@@ -603,8 +603,11 @@ export class Completer extends Widget {
       docPanel.setAttribute('style', 'display:none');
       return;
     }
+    docPanel.textContent = '';
     if (activeItem.documentation) {
-      docPanel.textContent = activeItem.documentation;
+      let pre = document.createElement('pre');
+      pre.textContent = activeItem.documentation;
+      docPanel.appendChild(pre);
       docPanel.setAttribute('style', '');
     } else {
       docPanel.setAttribute('style', 'display:none');

packages/completer/style/base.css

@@ -35,6 +35,12 @@
   );
 }
 
+.jp-Completer-docpanel pre {
+  border: none;
+  margin: 0px;
+  padding: 0px;
+}
+
 .jp-Completer-list {
   margin: 0;
   padding: 0;