feat: added support for image editing and upscaling for imagen3

[pavelgj]

  const baseImg = fs.readFileSync('base.png', { encoding: 'base64' });
  const maskImg = fs.readFileSync('mask.png', { encoding: 'base64' });

  const response = await ai.generate({
    model: imagen3,
    output: { format: 'media' },
    prompt: [
      { media: { url: `data:image/png;base64,${baseImg}` }},
      {
        media: { url: `data:image/png;base64,${maskImg}` },
        metadata: { type: 'mask' },
      },
      { text: 'replace the background with foo bar baz' },
    ],
    config: {
      editConfig: {
        editMode: 'outpainting',
      },
    },
  });

  return response.media();