Caption property is now supported for code block type

We have added support for adding, updating, and retrieving the caption property for code block types.

Below is an example response from append block children containing a code block, with a caption, uploaded to Notion.

{
    "object": "list",
    "results": [
        {
            "object": "block",
            "id": "block-id",
            "created_time": "2021-10-14T18:10:00.000Z",
            "last_edited_time": "2021-10-14T18:10:00.000Z",
            "has_children": false,
            "archived": false,
            "type": "code",
            "code": {
                "caption": [
                    {
                        "type": "text",
                        "text": {
                            "content": "Hello Caption!",
                            "link": null
                        },
                        "annotations": {
                            "bold": false,
                            "italic": false,
                            "strikethrough": false,
                            "underline": false,
                            "code": false,
                            "color": "default"
                        },
                        "plain_text": "Hello Caption!",
                        "href": null
                    }
                ],
                "text": [
                    {
                        "type": "text",
                        "text": {
                            "content": "const foo = \"bar\"",
                            "link": null
                        },
                        "annotations": {
                            "bold": false,
                            "italic": false,
                            "strikethrough": false,
                            "underline": false,
                            "code": false,
                            "color": "default"
                        },
                        "plain_text": "const foo = \"bar\"",
                        "href": null
                    }
                ],
                "language": "javascript"
            }
        },
    ],
    "next_cursor": null,
    "has_more": false
}