Create the best bounded reader available in the current execution context: a SyncFileSliceReader inside a Web Worker (where FileReaderSync exists), otherwise an async-only FileSliceReader.
FileReaderSync
The File or Blob to read from.
File
Blob
A reader over blob; test it with isSyncReader.
blob
Create the best bounded reader available in the current execution context: a SyncFileSliceReader inside a Web Worker (where
FileReaderSyncexists), otherwise an async-only FileSliceReader.