Add built-in middleware (directMention) document

[andrewdietrich]

Summary

Fixes #242. Updates docs with example of directMention and further details.

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.

[codecov]

Codecov Report

Merging #756 (1a20b8f) into main (dfc61e7) will not change coverage.
The diff coverage is n/a.

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[shaydewael]

Hey @andrewcashmore 👋 thanks for the PR. I took a look, and definitely agree that there should be more clarity around how default listeners like directMention() work. However, I don't think we should make the custom listener explanation secondary since the Listener Middleware section is really intended to explain how developers can build custom listener middleware (similar to the framing of Global Middleware). The builtin middleware is quite limited and doesn't support the majority of developer uses of listener middleware (like validating that the user invoking the event has relevant permissions, or injecting additional information in the context object).

That said, we should surface the information you've included here, and keep the edit about the mention being at the beginning of the message because I think that's a helpful addition. But I think a better home for the rest may be in the reference documentation, which could explicitly list and explain a variety of built-in middleware (including directMention()).

[CLAassistant]

All committers have signed the CLA.

[seratch]

But I think a better home for the rest may be in the reference documentation, which could explicitly list and explain a variety of built-in middleware (including directMention()).

I agree with this.

@andrewdietrich If you are still interested in working on this and you're fine to move this (and other built-in middleware too if possible..), it'd be appreciated 🙇

[seratch]

👋 To better manage tasks in this project, we are closing inactive issues and pull requests.

As we discussed above, we may add documents about built-in middleware as part of the Reference guide in the future. If you are still interested in making the document addition, we are happy to work together with you!

Thanks again for taking the time to make this pull request 🙇