Docs: Add props documentation to FileUpload component (#27393)

packages/grafana-ui/src/components/FileUpload/FileUpload.tsx

@@ -6,10 +6,13 @@ import { stylesFactory, useTheme } from '../../themes';
 import { ComponentSize } from '../../types/size';
 
 export interface Props {
+  /** Callback function to handle uploaded file  */
   onFileUpload: (event: FormEvent<HTMLInputElement>) => void;
   /** Accepted file extensions */
   accept?: string;
+  /** Overwrite or add to style */
   className?: string;
+  /** Button size */
   size?: ComponentSize;
 }