chore(v2): add stylelint (#2361)

* Add stylelint

* Add custom stylelint plugin for copyright

* Add stylelint to FB template

packages/stylelint-copyright/index.js

@@ -0,0 +1,55 @@
+/**
+ * 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 stylelint = require('stylelint');
+
+const ruleName = 'plugin/stylelint-copyright';
+const messages = stylelint.utils.ruleMessages(ruleName, {
+  rejected: 'Unexpected missing copyright in the first comment',
+});
+
+module.exports = stylelint.createPlugin(ruleName, actual => {
+  return (root, result) => {
+    const validOptions = stylelint.utils.validateOptions(result, ruleName, {
+      actual,
+    });
+
+    if (!validOptions) {
+      return;
+    }
+
+    root.walkComments(comment => {
+      // ignore root comments with copyright text
+      if (
+        comment === comment.parent.first &&
+        /[Cc]opyright/.test(comment.text)
+      ) {
+        return;
+      }
+
+      // ignore non-root comments
+      if (comment.type !== 'root' && comment !== comment.parent.first) {
+        return;
+      }
+
+      // ignore indented comments
+      if (comment.source.start.column > 1) {
+        return;
+      }
+
+      stylelint.utils.report({
+        message: messages.rejected,
+        node: comment,
+        result,
+        ruleName,
+      });
+    });
+  };
+});
+
+module.exports.ruleName = ruleName;
+module.exports.messages = messages;