adding alert component

src/widgets/alert.jsx

@@ -0,0 +1,28 @@
+import React from 'react';
+import { FormattedMessage } from 'react-intl';
+
+export default class Alert extends React.PureComponent {
+  render() {
+    return this.props.visible ?
+      <div className="alert-container">
+        <div className="alert">
+          <div className="title">{this.props.title}</div>
+          <div className="content">{this.props.content}</div>
+          <div className="dialog-buttons">
+            {this.props.onReject ?
+              <button className="outline" onClick={this.props.onReject}>
+                {this.props.reject || <FormattedMessage id="button_cancel" />}
+              </button>
+              :
+              null
+            }
+            <button className="blue" onClick={this.props.onConfirm}>
+              {this.props.confirm || <FormattedMessage id="button_ok" />}
+            </button>
+          </div>
+        </div>
+      </div>
+    :
+    null;
+  }
+};