docs: add alumni section to about page

[markostanimirovic]

PR Checklist

Please check if your PR fulfills the following requirements:

• [x] The commit message follows our guidelines: https://github.com/ngrx/platform/blob/main/CONTRIBUTING.md#commit
• [ ] Tests for the changes have been added (for bug fixes / features)
• [ ] Documentation has been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[x] Documentation content changes
[ ] Other... Please describe:

Does this PR introduce a breaking change?

[ ] Yes
[x] No

[netlify[bot]]

✅ Deploy Preview for ngrx-io ready!

Name	Link
🔨 Latest commit	092e65dd6cdd336182eb80dfbd8705d4bbb5c1b5
🔍 Latest deploy log	https://app.netlify.com/sites/ngrx-io/deploys/666b0dc036fadd0009f840f3
😎 Deploy Preview	https://deploy-preview-4389--ngrx-io.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.