feat: allow user to drag-n-drop audio clip into audio tracks; added m4a support

src/util/audioImportUtil.ts

@@ -0,0 +1,18 @@
+export const AUDIO_IMPORT_ACCEPTED_TYPES = ['.wav', '.mp3', '.ogg', '.flac', '.aac', '.m4a'] as const;
+
+export function getAudioImportExtension(fileOrName: File | string): string {
+  const fileName = typeof fileOrName === 'string' ? fileOrName : fileOrName.name;
+  return `.${fileName.split('.').pop()?.toLowerCase() ?? ''}`;
+}
+
+export function isAcceptedAudioImportFile(file: File): boolean {
+  return AUDIO_IMPORT_ACCEPTED_TYPES.includes(getAudioImportExtension(file) as typeof AUDIO_IMPORT_ACCEPTED_TYPES[number]);
+}
+
+export function getAudioImportDecodeFailureMessage(fileName: string): string {
+  if (getAudioImportExtension(fileName) === '.m4a') {
+    return `Unable to import "${fileName}". This browser could not decode the file's audio codec. M4A import depends on browser support.`;
+  }
+
+  return `Unable to import "${fileName}". This browser could not decode the selected audio file.`;
+}