feat: add Issue and PR duplicate detection bot

[Copilot]

Adds a GitHub Actions workflow that automatically triages new issues and PRs by detecting duplicates using Jaccard keyword similarity and posting contextual comments.

Workflow: .github/workflows/issue-pr-bot.yml

• Triggers on issues: [opened] and pull_request: [opened]
• Tokenises title + body — strips punctuation and stop-words to produce a keyword set
• Computes Jaccard similarity against all existing open issues/PRs; threshold is 0.30
• Duplicate path: adds duplicate label + comment pointing to the matched item number
• Non-duplicate path: adds needs-triage label + welcome comment with contribution guidance
• Both labels are auto-created if absent (idempotent)

Similarity logic

// Jaccard: |A ∩ B| / |A ∪ B|  — returns 0 if either set is empty
function jaccardSimilarity(setA, setB) {
  if (setA.size === 0 || setB.size === 0) return 0;
  const intersection = [...setA].filter(w => setB.has(w)).length;
  return intersection / new Set([...setA, ...setB]).size;
}

All logic runs inside a single actions/github-script@v7 step — no external dependencies or secrets beyond the default GITHUB_TOKEN.

[github-actions]

👋 Hello! Thanks for your contribution. We will review this and get back to you as soon as possible. — th30d4y

[github-actions]

👋 Thanks for opening this Pull Request!

A maintainer will review it shortly. In the meantime:

• Please make sure your description is as detailed as possible.
• Search existing issues at https://github.com/th30d4y/automation-hub/issues to avoid duplicates.
• Follow the contribution guidelines if they apply.