build: include the package lockfile for custom receiver example

[zimeg]

Summary

This PR adds the package-lock.json file to the custom receivers example to pin the following dependencies:

• @koa/[email protected]

To workaround an issue with the latest 15.1.0 release:

Error: src/KoaReceiver.ts(57,12): error TS2749: 'Router' refers to a value, but is being used as a type here. Did you mean 'typeof Router'?
Error: src/KoaReceiver.ts(90,19): error TS2749: 'Router' refers to a value, but is being used as a type here. Did you mean 'typeof Router'?
Error: src/KoaReceiver.ts(167,65): error TS7006: Parameter 'ctx' implicitly has an 'any' type.
Error: src/KoaReceiver.ts(170,69): error TS7006: Parameter 'ctx' implicitly has an 'any' type.
Error: src/KoaReceiver.ts(175,40): error TS7006: Parameter 'ctx' implicitly has an 'any' type.

🔗 https://github.com/slackapi/bolt-js/actions/runs/20244019276/job/58119249807#step:6:8

Notes

• Other examples within this repo don't include a package lock file, but I am open to revisiting this in follow up PRs! FWIW I think we should pin dependencies of example code

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

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.44%. Comparing base (d6f9ce7) to head (7011bd0).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2744   +/-   ##
=======================================
  Coverage   93.44%   93.44%           
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  Files          37       37           
  Lines        7675     7675           
  Branches      669      669           
=======================================
  Hits         7172     7172           
  Misses        498      498           
  Partials        5        5           

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[zimeg]

🗣️ A comment on change below for kind reviewers alike:

[zimeg]

👁️‍🗨️ note: Noticed that we can perhaps prefer the koa typings here!

@koa/router is written in TypeScript and includes comprehensive type definitions out of the box. No need for @types/* packages!

🔗 https://github.com/koajs/router?tab=readme-ov-file#typescript-support

[srtaalej]

⭐ ⭐ ⭐

[zimeg]

@srtaalej Woo! The stars are so appreciated 🤩 🌃 ✨

I'll merge this now to unblock CI for adjacent changes, but am keeping note that we might want to revisit the lockfile of other contained examples. Let's let @dependabot make this next update!