Add windows-dev-yaml to test new factory on Windows

The initial deployment worked on all builders except Windows,
so add a test builder to iron out the kinks.

buildbot/master/files/config/master.cfg

@@ -75,6 +75,7 @@ c['schedulers'].append(schedulers.AnyBranchScheduler(
         "mac-rel-wpt1",
         "mac-rel-wpt2",
         "windows-dev",
+        "windows-dev-yaml",
     ],
     change_filter=util.ChangeFilter(filter_fn=servo_auto_try_filter),
 ))
@@ -104,6 +105,7 @@ c['schedulers'].append(schedulers.ForceScheduler(
         "mac-rel-wpt1",
         "mac-rel-wpt2",
         "windows-dev",
+        "windows-dev-yaml",
         "windows-nightly",
     ],
 ))
@@ -195,8 +197,12 @@ c['builders'] = [
         factory=factories.doc,
     ),
     # Testing the In Tree YAML build
-    DynamicServoYAMLBuilder("linux-dev-yaml", LINUX_SLAVES,
-                            envs.build_linux)
+    DynamicServoYAMLBuilder(
+        "linux-dev-yaml", LINUX_SLAVES, envs.build_linux
+    ),
+    DynamicServoYAMLBuilder(
+        "windows-dev-yaml", WINDOWS_SLAVES, envs.build_windows
+    ),
 ]