text: Title: Support all possible fields for RichTextElementParts.Date 
  Body: The `slack_sdk.models.blocks.RichTextElementsParts.Date` type supports `timestamp`, but the actual "date" rich text element supports other fields like `url`, `fallback`, `format`. Can this be extended to properly support all available fields?
  
  documentation: https://api.slack.com/reference/block-kit/blocks#rich_text:~:text=date-,The%20following%20are%20the%20properties%20of%20the,object%20type,-in%20the
  
  
  block builder example: https://app.slack.com/block-kit-builder/TG4KUE8JV#%7B%22blocks%22:%5B%7B%22type%22:%22rich_text%22,%22elements%22:%5B%7B%22type%22:%22rich_text_section%22,%22elements%22:%5B%7B%22type%22:%22date%22,%22timestamp%22:1720710212,%22format%22:%22%7Bdate_num%7D%20at%20%7Btime%7D%22,%22fallback%22:%22timey%22%7D%5D%7D%5D%7D%5D%7D
  
  vs actual type in slack_sdk library:
  https://github.com/slackapi/python-slack-sdk/blob/main/slack_sdk/models/blocks/block_elements.py#L2097-L2112
  
  ### Category (place an `x` in each of the `[ ]`)
  
  - [ ] **slack_sdk.web.WebClient (sync/async)** (Web API client)
  - [ ] **slack_sdk.webhook.WebhookClient (sync/async)** (Incoming Webhook, response_url sender)
  - [x] **slack_sdk.models** (UI component builders)
  - [ ] **slack_sdk.oauth** (OAuth Flow Utilities)
  - [ ] **slack_sdk.socket_mode** (Socket Mode client)
  - [ ] **slack_sdk.audit_logs** (Audit Logs API client)
  - [ ] **slack_sdk.scim** (SCIM API client)
  - [ ] **slack_sdk.rtm** (RTM client)
  - [ ] **slack_sdk.signature** (Request Signature Verifier)
  
  ### Requirements
  
  Please read the [Contributing guidelines](https://github.com/slackapi/python-slack-sdk/blob/main/.github/contributing.md) and [Code of Conduct](https://slackhq.github.io/code-of-conduct) before creating this issue or pull request. By submitting, you are agreeing to those rules.
  