Module callbacks 
Source - FileReader
- A guard object that aborts the file read when dropped (if the read isn’t already
finished).
- read_as_array_buffer
- Asynchronously converts the blobinto an array buffer and then passes it to thecallback.
- read_as_bytes
- Asynchronously converts the blobinto aVec<u8>and then passes it to thecallback.
- read_as_data_url
- Asynchronously converts the blobinto a base64 encodeddata:URL and then passes it to
thecallback.
- read_as_text
- Asynchronously converts blobinto a text string and then passes it to thecallback.