Style refinements to collaborator hover.

packages/codemirror/style/index.css

@@ -82,8 +82,12 @@
   transform: translateX(-50%);
   color: white;
   border-radius: 3px;
-  padding: 1px;
+  padding-left: 4px;
+  padding-right: 4px;
+  padding-top: 1px;
+  padding-bottom: 1px;
   text-align: center;
+  font-size: var(--jp-ui-font-size1);
   white-space: nowrap;
 }