Slack-sdk

Mainly for the deprecation notice in the PyPI package page: https://pypi.org/project/slackclient/

Here is [the list of issues](https://github.com/slackapi/python-slack-sdk/milestone/25?closed=1) for the release.

Refer to [v2.9.3 milestone](https://github.com/slackapi/python-slackclient/milestone/20?closed=1) to know the complete list of the issues resolved by this release.

**Updates**

1. [Block Kit] 851 852 Set default_type for HeaderBlock text - Thanks fwump38
2. [Block Kit] 853 854 Enable to use input blocks in Home tab views - Thanks fwump38
3. [RTMClient] 857 846 RTMClient does not pass timeout value to WebClient - Thanks Luden seratch

Refer to [v2.9.2 milestone](https://github.com/slackapi/python-slackclient/milestone/19?closed=1) to know the complete list of the issues resolved by this release.

**Updates**

1. [Block Kit] 841 Dispatch Action in Input blocks - Thanks seratch
2. [WebClient] 838 Add apps.event.authorizations.list and other APIs - Thanks seratch
3. [WebClient][WebhookClient] 829 Improve error body parser to handle no charset responses - Thanks adamchainz seratch
4. [Block Kit] 824 Correct text field validation in Header blocks - Thanks seratch

This is a hotfix release for the issue with `proxy` option in `WebClient`, `WebhookClient` constructors.

If your app is affected by this issue, please consider taking either of the following actions:

1) **Upgrade to this version (2.9.1)** (no code change required in this case)
2) If there is a reason to avoid upgrading at this moment, **switch to the standard `HTTPS_PROXY` environment variable and stop using the `proxy` option**. The env variable should work regardless of the `slackclient` versions.

We're sorry for causing trouble and inconvenience.

Refer to [v2.9.1 milestone](https://github.com/slackapi/python-slackclient/milestone/18?closed=1) to know the complete list of the issues resolved by this release.

**Updates**

1. [WebClient][WebhookClient] 820 821 822 The proxy option in WebClient/WebhookClient no longer works - Thanks seratch