fix: adding files count in toast (#960)

* fix: adding files count in toast

* fix: toast to use plural function

src/files-and-videos/generic/FileInput.jsx

@@ -11,7 +11,7 @@ export const useFileInput = ({
   const click = () => ref.current.click();
   const addFile = (e) => {
     const { files } = e.target;
-    setSelectedRows(files);
+    setSelectedRows([...files]);
     onAddFile(Object.values(files));
     setAddOpen();
     e.target.value = '';

src/files-and-videos/generic/messages.js

@@ -8,7 +8,7 @@ const messages = defineMessages({
   },
   apiStatusToastMessage: {
     id: 'course-authoring.files-and-upload.apiStatus.message',
-    defaultMessage: '{actionType} {selectedRowCount} {fileType}(s)',
+    defaultMessage: '{actionType} {selectedRowCount} {selectedRowCount, plural, one {{fileType}} other {{fileType}s}}',
     description: 'This message is showed in the toast when action is applied to files',
   },
   apiStatusAddingAction: {