appveyor.yml: customize icon_url

We're using "x" sign as an icon for incoming webhook, but the success
notification by `on_build_status_changed` should not be an "x" asign.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64311 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

appveyor.yml

@@ -64,12 +64,13 @@ for:
       url:
         secure: iMINHMS0nZabaDsxN9omRDsekxzVvAAzEq5ev7lN6vZ6r9zNhl3/F/7POIVyahAwVFpRDeQT/iUugpAGWmOt3eGL/lZIdqiJFZ9DjPSkP68= # #alerts
       method: POST
+      # "icon_url" is the url used by `provider: Slack`
       body: >-
         {{^isPullRequest}}
           {
             "attachments": [
               {
-                "title": "AppVeyor Build {{projectName}} {{buildVersion}} {{status}}",
+                "title": "Build {{projectName}} {{buildVersion}} {{status}}",
                 "fallback": "AppVeyor Build {{projectName}} {{buildVersion}} {{status}}",
                 "title_link": "{{buildUrl}}",
                 "text": "Commit <{{commitUrl}}|{{commitId}}> by {{commitAuthor}} on {{commitDate}}: _{{commitMessage}}_",
@@ -80,7 +81,9 @@ for:
                   "color": "#ee4444"
                 {{/failed}}
               }
-            ]
+            ],
+            "icon_url": "https://slack-files2.s3-us-west-2.amazonaws.com/bot_icons/2018-02-10/314363543719_48.png",
+            "username": "AppVeyor CI"
           }
         {{/isPullRequest}}
       on_build_success: false