message: exporting Exceptions + fix some browser exports
diff: // browser
  -export * from './browser/BrowserCodeReader';
  export * from './browser/BrowserQRCodeReader';
  export * from './browser/BrowserDatamatrixCodeReader';
  export * from './browser/BrowserQRCodeSvgWriter';
  -export * from './browser/HTMLCanvasElementLuminanceSource';
  -export * from './browser/VideoInputDevice';
  export * from './browser/BrowserBarcodeReader';
  +export { default as BrowserCodeReader } from './browser/BrowserCodeReader';
  +export { default as HTMLCanvasElementLuminanceSource } from './browser/HTMLCanvasElementLuminanceSource';
  +export { default as VideoInputDevice } from './browser/VideoInputDevice';
  +
  +// Exceptions
  +export { default as Exception } from './core/Exception';
  +export { default as ArgumentException } from './core/ArgumentException';
  +export { default as ArithmeticException } from './core/ArithmeticException';
  +export { default as ChecksumException } from './core/ChecksumException';
  +export { default as FormatException } from './core/FormatException';
  +export { default as IllegalArgumentException } from './core/IllegalArgumentException';
  +export { default as IllegalStateException } from './core/IllegalStateException';
  +export { default as NotFoundException } from './core/NotFoundException';
  +export { default as ReaderException } from './core/ReaderException';
  +export { default as ReedSolomonException } from './core/ReedSolomonException';
  +export { default as UnsupportedOperationException } from './core/UnsupportedOperationException';
  +export { default as WriterException } from './core/WriterException';
  // core
  export { default as BarcodeFormat } from './core/BarcodeFormat';
  export { default as Binarizer } from './core/Binarizer';
  export { default as BinaryBitmap } from './core/BinaryBitmap';
  export { default as DecodeHintType } from './core/DecodeHintType';
  -export { default as Exception } from './core/Exception';
  export { default as InvertedLuminanceSource } from './core/InvertedLuminanceSource';
  export { default as LuminanceSource } from './core/LuminanceSource';
  export { default as MultiFormatReader } from './core/MultiFormatReader';
  