package:webcrypto version 0.6.1

• Added Dart native build hooks and native asset lookup for the bundled
  native library, enabling dart test for the core package.
• webcrypto is now packaged as a Dart package using native hooks instead of
  Flutter plugin scaffolding.
• Improved web error handling when window.crypto.subtle is unavailable in
  insecure contexts by throwing a clearer UnsupportedError with guidance.
• Added documentation for performing deriveKey using deriveBits and
  importRaw.