sticky download button so long previews doesn't push buttons down, closes #205

components/previews/TextPreview.tsx

@@ -23,14 +23,14 @@ const TextPreview: FunctionComponent<{ file: any }> = ({ file }) => {
   }
 
   return (
-    <>
+    <div>
       <div className="dark:bg-gray-900 dark:text-gray-100 p-3 bg-white rounded">
         <pre className="md:p-3 p-0 overflow-scroll">{data}</pre>
       </div>
-      <div className="mt-4">
+      <div className="border-t-gray-200 dark:border-t-gray-700 border-t p-2 sticky bottom-0 left-0 right-0 z-10 bg-white bg-opacity-80 backdrop-blur-md dark:bg-gray-900">
         <DownloadButtonGroup downloadUrl={file['@microsoft.graph.downloadUrl']} />
       </div>
-    </>
+    </div>
   )
 }