fix: add mimetype when create blob

[everywill]

No description provided.

[reklawnos]

@everywill What's the particular issue this solves? This currently copies the behavior of worker-loader, which does not specify a mimetype when creating the blob.

[everywill]

When try worklet-loader with options: { inline:true}, chrome doesn't accept the generated blob as worklet. It seems that
only explicitly assigned with the mime-type, the blob can be executed as worklet.

[lawrence-witt]

I'd like to second this. I get DOMException: The user aborted a request when trying to run inline Audio Worklets in Chromium browsers without specifying the mimetype.

It makes sense that this would deviate from Web Workers since Audio Worklets are only supposed to be run in a secure context, however AFAIK only Chrome is currently implementing that part of the spec.