Add renovate security-updates-only configuration

[dakujem]

This PR adds renovate.json, as suggested in https://github.com/laminas/laminas-xml/issues/12.

The file only refs the laminas/.github configuration.

[internalsystemerror]

I have all these queued and waiting to push locally, but I'm still waiting on the README.md wording updates from @weierophinney and the autocloser XML from @Xerkus.

[dakujem]

I pushed the updated renovate.json that points to renovate-config-security-updates-only.

[internalsystemerror]

Also, It's not really as simple as just enabling renovate, as renovate relies on CI checks to tell it whether the upgrade is OK or not. So I've also been looking at getting all these security only packages to at least use PHPUnit + Psalm.

[Ocramius]

@internalsystemerror so we should hold off? 🤔

[internalsystemerror]

I'm on the fence tbh... I'm not convinced that PHPUnit alone will protect us from breaks in this repository. If you feel differently then overrule me, but I would rather we shore up the CI checks on these libs prior to enabling renovate.

Although the security only configuration doesn't automerge anything so it may be safe to do so anyway.

[Ocramius]

I'm happy with PHPUnit only here, FWIW 👍

[dakujem]

Nice. I have no idea what I've done, but I'm glad it was what you guys wanted 😅

Thanks for maintaining the packages 💪

[internalsystemerror]

@dakujem Thanks for the contribution!