fix(v2): improve stylelint copyright header rule (#2363)

* fix(v2): improve stylelint copyright header rule

* Whitelist stylelint-copyright from Jest

packages/stylelint-copyright/tests/index.js

@@ -0,0 +1,58 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+const testRule = require('stylelint-test-rule-tape');
+const stylelintCopyright = require('..');
+
+testRule(stylelintCopyright.rule, {
+  ruleName: stylelintCopyright.ruleName,
+  accept: [
+    {
+      code: `
+/**
+ * Copyright
+ */
+
+ .foo {}`,
+    },
+    {
+      code: `
+      /**
+ * copyright
+ */
+
+ .foo {}`,
+    },
+  ],
+  reject: [
+    {
+      code: `
+/**
+ * Copyleft
+ */
+
+ .foo {}`,
+      message: `Missing copyright in the header comment (${stylelintCopyright.ruleName})`,
+      line: 2,
+      column: 1,
+    },
+    {
+      code: `
+/**
+ * Copyleft
+ */
+
+/**
+ * Copyright
+ */
+ .foo {}`,
+      message: `Missing copyright in the header comment (${stylelintCopyright.ruleName})`,
+      line: 2,
+      column: 1,
+    },
+  ],
+});