Add localization framework for the GUI (en-US baseline) (#764)

Credit to @jmolinap2 for their work in #643, which was used as inspiration.

Tests/TestData/LanguageLoading/en-US/Categories.json

@@ -0,0 +1,5 @@
+{
+  "PrivacySuggestedContent": {
+    "Label": "Privacy & Suggested Content"
+  }
+}

Tests/TestData/LanguageLoading/en-US/Chrome.json

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+{
+  "TitleBarClose": "Close",
+  "TitleBarOptions": "Options",
+  "AppsSelectedCount_one": "{0} app selected",
+  "AppsSelectedCount_other": "{0} apps selected",
+  "TooManyPlaceholders": "Value is {0} and {1}"
+}

Tests/TestData/LanguageLoading/en-US/Features.json

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+{
+  "Features": {
+    "DisableTelemetry": {
+      "Label": "Disable telemetry",
+      "ToolTip": "Disables telemetry collection."
+    },
+    "ClearStart": {
+      "Label": "Remove for the selected user"
+    }
+  },
+  "UiGroups": {
+    "SearchIcon": {
+      "Label": "Taskbar search style"
+    },
+    "ClearStart": {
+      "Label": "Remove pinned apps from the start menu",
+      "ToolTip": "This setting allows you to quickly remove all pinned apps from the start menu."
+    }
+  }
+}

Tests/TestData/LanguageLoading/es-ES/Categories.json

@@ -0,0 +1 @@
+{}

Tests/TestData/LanguageLoading/es-ES/Chrome.json

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+{
+  "TitleBarClose": "Cerrar"
+}

Tests/TestData/LanguageLoading/es-ES/Features.json

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+{
+  "Features": {},
+  "UiGroups": {}
+}