Adds Mattermost label and icon to new group form

app/assets/stylesheets/pages/groups.scss

@@ -73,3 +73,9 @@
     }
   }
 }
+
+.mattermost-icon svg{
+  width: 16px;
+  height: 16px;
+  vertical-align: text-bottom;
+}

app/views/groups/new.html.haml

@@ -17,9 +17,15 @@
   = render 'shared/visibility_level', f: f, visibility_level: default_group_visibility, can_change_visibility_level: true, form_model: @group
 
   .form-group
-    = f.label :create_chat_team, "Create Mattermost Team", class: 'control-label'
+    = f.label :create_chat_team, class: 'control-label' do
+      %span.mattermost-icon
+        = custom_icon('icon_mattermost')
+      Mattermost
     .col-sm-10
-      = f.check_box :chat_team
+      .checkbox
+        = f.label :chat_team do
+          = f.check_box :chat_team
+          Link the group to a new or existing Mattermost team
 
   .form-group
     .col-sm-offset-2.col-sm-10

app/views/shared/icons/_icon_mattermost.svg

+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 500 500"><path d="M250.05 34c1.9.04 3.8.11 5.6.2l-29.79 35.51c-.07.01-.15.03-.23.04C149.26 84.1 98.22 146.5 98.22 222.97c0 41.56 23.07 90.5 59.75 119.1 28.61 22.32 64.29 36.9 101.21 36.9 93.4 0 160.15-68.61 160.15-156 0-34.91-15.99-72.77-41.76-100.76l-1.63-47.39c54.45 39.15 89.95 103.02 90.06 175.17v.01c0 119.29-96.7 216-216 216-119.29 0-216-96.71-216-216S130.71 34 250 34h.05zm64.1 20.29c.66-.04 1.32.03 1.96.25 3.01 1 3.85 3.57 3.93 6.45l3.84 146.88c.76 28.66-17.16 68.44-60.39 68.56-30.97.08-63.68-20.83-63.68-60.13.01-14.73 5.61-31.26 19.25-48.11l90.03-111.18c1.15-1.42 3.08-2.58 5.06-2.72z"/></svg>
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