Add test for maps

tests/maps.js

@@ -0,0 +1,21 @@
+type Type = {
+    [string]: number,
+};
+
+interface Interface {
+    [string]: number;
+}
+
+// ###
+({
+    Type: {
+        type: 'map',
+        name: 'Type',
+        values: 'double',
+    },
+    Interface: {
+        type: 'map',
+        name: 'Interface',
+        values: 'double',
+    },
+});