Investigate say() and respond()

[kronosapiens]

Bolt JS provides some helper functions for responding to requests. If I can use these instead of my own postMessage or postEphemeral functions the codebase can be kept more semantic.

https://slack.dev/bolt-js/concepts

[kronosapiens]

In #239 , respond was used to replace the existing replyEphemeral. Looking into say, however, it seems as though there are fewer, if any, opportunities to use it. say is a helper meant to respond to message events -- such as when the app is directly mentioned, or a specific emoji is triggered. These are not flows which we utilize, so we have limited use for say.