docs: list flags before examples in generated reference

[zimeg]

Summary

This PR lists flags before examples in generated reference to match outputs of the --help commands 🤖

Preview

The following page and command might demonstrate the purpose of this change:

• Docs: https://docs.slack.dev/tools/slack-cli/reference/commands/slack_app_link
• CLI: slack app link --help

Reviewers

The generated outputs aren't included in this PR but can be found with these commands:

$ make build && PATH="./bin" slack docgen docs/reference
$ git diff

Requirements

• 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

❌ Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 62.94%. Comparing base (2de192d) to head (7180327).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
cmd/docgen/docgen.go	0.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@ Coverage Diff @@## main #195 +/- ##
==========================================
+ Coverage 62.91% 62.94% +0.03% 
==========================================
Files 212 212 Lines 21782 21782 ==========================================
+ Hits 13704 13711 +7 + Misses 7014 7009 -5 + Partials 1064 1062 -2 

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[mwbrooks]

✅ Much better! Thank you 🙇🏻

[lukegalbraithrussell]

🎈

[zimeg]

@mwbrooks@lukegalbraithrussell Thank y'all too. The docs continue to find incredible improvements all around - I hope this can be considered with such changes 🎁