New timeline items query and mutations

The platform API will support the Emails & Activities (E&A) app in API versions 2024-10 and later. We added the following queries to read, create, and delete timeline items in the E&A app:

• timeline_item query
• create_timeline_item mutation
• delete_timeline_item mutation

query {
  timeline_item (id: "6376175611") {
    board {
      id
    }
    item {
      name
    }
    id
    ref_id
    user {
      id
      name
    }
    title
    type
  }
}