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

app/javascript/mastodon/components/loading_indicator.jsx

@@ -0,0 +1,32 @@
+import React from 'react';
+import PropTypes from 'prop-types';
+
+export const CircularProgress = ({ size, strokeWidth }) => {
+  const viewBox = `0 0 ${size} ${size}`;
+  const radius  = (size - strokeWidth) / 2;
+
+  return (
+    <svg width={size} height={size} viewBox={viewBox} className='circular-progress' role='progressbar'>
+      <circle
+        fill='none'
+        cx={size / 2}
+        cy={size / 2}
+        r={radius}
+        strokeWidth={`${strokeWidth}px`}
+      />
+    </svg>
+  );
+};
+
+CircularProgress.propTypes = {
+  size: PropTypes.number.isRequired,
+  strokeWidth: PropTypes.number.isRequired,
+};
+
+const LoadingIndicator = () => (
+  <div className='loading-indicator'>
+    <CircularProgress size={50} strokeWidth={6} />
+  </div>
+);
+
+export default LoadingIndicator;