Run format check in CI.

.config/dotnet-tools.json

@@ -13,6 +13,12 @@
       "commands": [
         "dotnet-format"
       ]
+    },
+    "codefilesanity": {
+      "version": "0.0.33",
+      "commands": [
+        "CodeFileSanity"
+      ]
     }
   }
 }

appveyor.yml

@@ -8,6 +8,10 @@ build:
   project: osu.sln
   parallel: true
   verbosity: minimal
+after_build:
+  - ps: dotnet tool restore
+  - ps: dotnet CodeFileSanity
+  - ps: dotnet format --dry-run --check
 test:
   assemblies:
     except: