v0.6.0

Added

• Add text flattening method for Content: Content::flatten_into_text(). <- (#1)
• Add image source flattening method for Content: Content::flatten_into_image_source().
• Add assistant message creation method for MessagesResponseBody: MessagesResponseBody::create_message().
• Add builder pattern for Client: ClientBuilder.
• Add an example to create a message with vision.
• Add an example to converse with the assistant.

Changed

• Rename StreamChunk to MessageChunk.
• Rename Content::MultipleBlock to Content::MultipleBlocks.
• Improve initialization and conversion methods for Content and Message.

Fixed

• Fix default value of the role field in the MessagesResponseBody from Role::user to Role::assistant.