Translate "Okay" in confirm dialogs

data/core.yaml

@@ -190,6 +190,8 @@ en:
     facebook: "Share on Facebook"
     tweet: "Tweet"
     okay: "Okay"
+  confirm:
+    okay: "Okay"
   splash:
     welcome: Welcome to the iD OpenStreetMap editor
     text: "iD is a friendly but powerful tool for contributing to the world's best free world map. This is version {version}. For more information see {website} and report bugs at {github}."

dist/locales/en.json

@@ -234,6 +234,9 @@
         "tweet": "Tweet",
         "okay": "Okay"
     },
+    "confirm": {
+        "okay": "Okay"
+    },
     "splash": {
         "welcome": "Welcome to the iD OpenStreetMap editor",
         "text": "iD is a friendly but powerful tool for contributing to the world's best free world map. This is version {version}. For more information see {website} and report bugs at {github}.",

js/id/ui/confirm.js

@@ -20,7 +20,7 @@ iD.ui.confirm = function(selection) {
         .on('click.confirm', function() {
             modal.remove();
         })
-        .text('Okay');
+        .text(t('confirm.okay'));
 
     return modal;
 };