Add in timezone property for timepicker element

[hello-ashleyintech]

Summary

Adding in a new timezone string property to the TimePicker block element. See #1249 for more info.

Along with adding in the new property in slack_sdk/models/blocks/block_elements.py, also updated and previewed the docs and added a unit test corresponding to the addition of this new property.

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)
• slack_sdk.socket_mode (Socket Mode client)
• slack_sdk.signature (Request Signature Verifier)
• slack_sdk.oauth (OAuth Flow Utilities)
• slack_sdk.models (UI component builders)
• slack_sdk.scim (SCIM API client)
• slack_sdk.audit_logs (Audit Logs API client)
• slack_sdk.rtm_v2 (RTM client)
• /docs-src (Documents, have you run ./scripts/docs.sh?)
• /docs-src-v2 (Documents, have you run ./scripts/docs-v2.sh?)
• /tutorial (PythOnBoardingBot tutorial)
• tests/integration_tests (Automated tests for this library)

Requirements (place an x in each [ ])

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've run python3 -m venv .venv && source .venv/bin/activate && ./scripts/run_validation.sh after making the changes.

[codecov]

Codecov Report

Merging #1251 (1ff0e0b) into main (2965fa1) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #1251   +/-   ##
=======================================
  Coverage   86.64%   86.64%           
=======================================
  Files         111      111           
  Lines       11025    11026    +1     
=======================================
+ Hits         9553     9554    +1     
  Misses       1472     1472           

Impacted Files	Coverage Δ
slack_sdk/models/blocks/block_elements.py	92.89% <100.00%> (+0.01%)	⬆️

📣 Codecov can now indicate which changes are the most critical in Pull Requests. Learn more

[seratch]

Thanks, LGTM but can you revert the document changes? We generate them when releasing a new version.

[seratch]

Thank you! LGTM