no-unused: add test for global augmentation

Author: ajafff

package.json

@@ -31,7 +31,7 @@
   "license": "MIT",
   "dependencies": {
     "tslib": "^1.7.1",
-    "tsutils": "^2.6.1"
+    "tsutils": "^2.8.2"
   },
   "devDependencies": {
     "coveralls": "^2.13.0",

test/rules/no-unused/default/mixed.lint

@@ -67,4 +67,8 @@ new (class T<T> {
 });
 new (class T {
     foo(): T {}
-})();
+})();
+
+declare global {
+    interface Foo {}
+}