Rename JSX files with proper .jsx extension (#23733)

app/javascript/mastodon/components/skeleton.jsx

@@ -0,0 +1,11 @@
+import React from 'react';
+import PropTypes from 'prop-types';
+
+const Skeleton = ({ width, height }) => <span className='skeleton' style={{ width, height }}>&zwnj;</span>;
+
+Skeleton.propTypes = {
+  width: PropTypes.oneOfType([PropTypes.number, PropTypes.string]),
+  height: PropTypes.oneOfType([PropTypes.number, PropTypes.string]),
+};
+
+export default Skeleton;