Add Slack Integration Test

[ataylorme]

Note: this test is currently failing. See #590

Perhaps this pull request to add a test can be used for test driven development to resolve the issue.

[styfle]

this test is currently failing

Looks like the test is passing CI now

[ataylorme]

Looks like the test is passing CI now

@styfle I updated the Slack dependency for this test case and while the test started passing here I am still experiencing the error outlined in #590 in my own code bases with the updated Slack SDK and ncc version 0.24.1. 0.23.0 does not have the issue.

I've recreated the issue with a unit test in https://github.com/ataylorme/ncc-0.24.1-slack-compilation-issue that actually uses the SDK, not just imports at as this test does.

[styfle]

The branch you're testing against here is newer than 0.24.1.

I tried with the latest ncc and it worked. So I'll go ahead and release a new version, thanks 👍

[ataylorme]

Okay, awesome, thank you @styfle. Once a new version of ncc is released I'll test it out. I'm looking forward to being on the latest and greatest!

edit: version 0.25.0 tested well with my more expanded unit test: https://github.com/ataylorme/ncc-0.24.1-slack-compilation-issue/runs/1359957476