- l10n: Add Chinese (simplified) extension locales (Thanks, @enlove!)

- Linting (ESLint): Avoid reporting `no-console`
- Refactoring: Avoid Firefox console errors with hidden iframe
- Docs (CHANGES): Fix Markdown heading level

editor/extensions/ext-locale/polygon/zh-CN.js

@@ -0,0 +1,14 @@
+export default {
+  name: '多边形',
+  buttons: [
+    {
+      title: '多边形工具'
+    }
+  ],
+  contextTools: [
+    {
+      title: '边数',
+      label: '边数'
+    }
+  ]
+};