Add Typescript example to securing-your-webhooks.md

[tycrimm]

Why:

The existing Securing your webhooks page includes examples for Python and Ruby, but not Typescript. This PR adds a Typescript example that hopefully saves X minutes off future webhook receivers that prefer to code in TS/JS.

Closes: 25789

What's being changed (if available, include any code snippets, screenshots, or gifs):

An example for verifying webhook payloads written in Typescript is included on the Securing your webhooks page

Check off the following:

• I have reviewed my changes in staging, available via the View deployment link in this PR's timeline.

  • For content changes, you will also see an automatically generated comment with links directly to pages you've modified. The comment won't appear if your PR only edits files in the data directory.

• For content changes, I have completed the self-review checklist.

[welcome]

Thanks for opening this pull request! A GitHub docs team member should be by to give feedback soon. In the meantime, please check out the contributing guidelines.

[github-actions]

Automatically generated comment ℹ️

This comment is automatically generated and will be overwritten every time changes are committed to this branch.

The table contains an overview of files in the content directory that have been changed in this pull request. It's provided to make it easy to review your changes on the staging site. Please note that changes to the data directory will not show up in this table.

---

Content directory changes

You may find it useful to copy this table into the pull request summary. There you can edit it to share links to important articles or changes and to give a high-level overview of how the changes in your pull request support the overall goals of the pull request.

Source	Preview	Production	What Changed
webhooks-and-events/webhooks/securing-your-webhooks.md	fpt ghec ghes@ 3.8 3.7 3.6 3.5 3.4 ghae	fpt ghec ghes@ 3.8 3.7 3.6 3.5 3.4 ghae

---

fpt: Free, Pro, Team
ghec: GitHub Enterprise Cloud
ghes: GitHub Enterprise Server
ghae: GitHub AE

[cmwilson21]

@tycrimm Thanks so much for opening a PR! I'll get this triaged for review ⚡

If you're looking for another issue to pick up while waiting, take a look at our help wanted section to find open issues you can work on. ✨

[skedwards88]

Thanks for adding this example! We'll get this merged down for you.

[github-actions]

Thanks very much for contributing! Your pull request has been merged 🎉 You should see your changes appear on the site in approximately 24 hours. If you're looking for your next contribution, check out our help wanted issues ⚡