H-5894: Update X handle to hashai

[vilkinsons]

🌟 What is the purpose of this PR?

Points to our updated X handle: x.com/hashai

[cursor]

PR Summary

Updates references to our X handle to ensure consistency.

• Changes x.com/hashintel → x.com/hashai in .github/ISSUE_TEMPLATE/config.yml
• Updates README contact link to https://x.com/hashai
• Points the frontend FollowUsButton to https://x.com/hashai in apps/hash-frontend/src/pages/index.page/shared/follow-us-button.tsx

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[augmentcode]

🤖 Augment PR Summary

Summary: Updates the project’s X (Twitter) handle references to point to @hashai.


Changes: Replaces the previous x.com/hashintel link in the GitHub issue template contact link, the repo README contact section, and the frontend “Follow us” CTA button.

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[augmentcode]

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