support icu messageformat for translations

build/intl-linter/rules/noLegacyVariables.ts

@@ -0,0 +1,17 @@
+// Copyright 2022 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { rule } from '../utils/rule';
+
+export default rule('noLegacyVariables', context => {
+  return {
+    enterLiteral(element) {
+      if (/(\$.+?\$)/.test(element.value)) {
+        context.report(
+          'String must not contain legacy $variables$',
+          element.location
+        );
+      }
+    },
+  };
+});