Adding hard-coded application header.

src/courseware/sequence/UnitButton.jsx

@@ -0,0 +1,30 @@
+import React from 'react';
+import classNames from 'classnames';
+import { Button } from '@edx/paragon';
+
+import UnitIcon from './UnitIcon';
+import CompleteIcon from './CompleteIcon';
+
+export default function UnitButton({
+  onClick,
+  pageTitle,
+  type,
+  isActive,
+  isComplete,
+}) {
+  return (
+    <Button
+      className={classNames({
+        active: isActive,
+        'btn-outline-primary': !isActive,
+        'btn-outline-secondary': isActive,
+      })}
+      disabled={isActive}
+      onClick={onClick}
+      title={pageTitle}
+    >
+      <UnitIcon type={type} />
+      {isComplete ? <CompleteIcon className="text-success ml-2" /> : null}
+    </Button>
+  );
+}