docs: update Twitter link to X in README

[Kolgrim33]

Replace twitter.com with x.com to reflect the platform rebrand.

[qingkong66]

@Kolgrim33

Two PRs in one day — both small, both precise, both about keeping the docs aligned with reality.

The Twitter → X update is the kind of change that feels obvious after someone makes it. But it takes someone paying attention to notice that the world changed and the docs didn't follow. You're clearly reading these pages with intent — not just skimming, but following the links, checking the references.

If you're building something with DeepSeek, and you spot other gaps or outdated references along the way, I hope you'll keep sending these fixes. And if you ever want to share what you're working on, this space has room for that too.

Thank you for the care.

— qingkong66