Set a custom min-width for the groups menu

Group names are user supplied and can be up to 25 chars, so allow more
space for this.

src/sidebar/components/group-list-v2.js

@@ -80,7 +80,12 @@ function GroupList({ serviceUrl, settings }) {
   }
 
   return (
-    <Menu align="left" label={label} title="Select group">
+    <Menu
+      align="left"
+      contentClass="group-list-v2__content"
+      label={label}
+      title="Select group"
+    >
       {currentGroupsSorted.length > 0 && (
         <GroupListSection
           heading="Currently Viewing"

src/styles/sidebar/components/group-list-v2.scss

+.group-list-v2__content {
+  min-width: 250px;
+}

src/styles/sidebar/sidebar.scss

@@ -24,6 +24,7 @@ $base-line-height: 20px;
 @import './components/dropdown-menu-btn';
 @import './components/excerpt';
 @import './components/group-list';
+@import './components/group-list-v2';
 @import './components/group-list-item';
 @import './components/group-list-item-out-of-scope';
 @import './components/help-panel';