Implement timestamp option for ios

[n1ru4l]

Implements #18

Code sample:

import RNThumbnail from 'react-native-thumbnail';
const timestampInSeconds = 3
RNThumbnail.get(filepath, { timestamp: timestampInSeconds }).then((result) => {
  console.log(result.path); // thumbnail path
})

[phuochau]

@n1ru4l I think the code example is wrong? The timestamp should be an option of get function

[n1ru4l]

@phuochau I updated the example, however the code is fully functional

[watadarkstar]

@n1ru4l What would happen if that frame / timestamp doesn't exist?

[n1ru4l]

@watadarkstar You will receive the last frame if the timestamp exceeds the maximum duration of the video.

@phuochau Is there anything further you need to be added before merging this?

Offtopic:

@phuochau Have you considered moving this repository over to react-native-community or adding additional maintainers? This could improve the quality and development of this library significantly.