Add more supports for cursor pagination

[hotwatermorning]

• Slack added cursor pagination options for some APIs on Aug 8th.
  • https://api.slack.com/docs/pagination
• To support cursor pagination for the APIs, update slack-api-ref and fix some methods in web/api/endpoints/*.rb.

[dblock]

We typically include the API changes here in CHANGELOG, please add.

The build is failing, needs 💚 , rubocop -a; rubocop --auto-gen-config.

Aren't the modified files for pagination auto-generated? They should not be altered by hand.

[hotwatermorning]

We typically include the API changes here in CHANGELOG, please add.

Let me see. Should the description of this changes in CHANGELOG.md be like this?

[#215](https://github.com/slack-ruby/slack-ruby-client/pull/215): Add cursor pagination support for `groups_list`, `files_info`, `mpim_list`, `reactions_list`, `stars_list` - [@hotwatermorning](https://github.com/hotwatermorning).

Excuse me, I had forgot to do rubocop --auto-gen-config.
Now I did the command, added changes of .rubocop_todo.yml into 3701595, and pushed.

[hotwatermorning]

Aren't the modified files for pagination auto-generated? They should not be altered by hand.

I see. The modified files are auto-generated by rake slack:api:update.

(I had altered them by hands. but these changes were overwritten by the command.)

[dblock]

Please update this with all the changes in separate items by looking at the diff. For example "Added apps_permissions_users_list" or "files_info, ... now support pagination". Thx.

[dblock]

This looks good. Update the changelog with all the changes and it's good to go.

[hotwatermorning]

Thank you for your kind advice.

I fixed the changelog and pushed. How about this?

[dblock]

Good, merged. Thanks.