[Improvement] Spell check only PR-changed files and added manual dispatch for full check

[richarddushime]

Description

This improves the spell check feature and Instead of commenting on every Pull Request , typos from other files

• PR triggers now only spell-check files changed in the PR (not entire site contents)
• Added workflow_dispatch with option to check all content manually
• Updated script to handle both modes with appropriate output messages

Type of Change

• New feature

Testing

• Tested locally
• Previewed on staging.forrt.org
• Not tested yet

Checklist

• Self-reviewed my changes
• Verified links and formatting are correct
• No new warnings or errors

Notes

[github-actions]

👍 All image files/references (if any) are in webp format, in line with our policy.

[github-actions]

✅ Spell Check Passed

No spelling issues found when checking 2 changed file(s)! 🎉

[LukasWallrich]

✅ Staging Deployment Status

This PR has been successfully deployed to staging as part of an aggregated deployment.

Deployed at: 2026-03-08 00:46:23 UTC
Staging URL: https://staging.forrt.org

The staging site shows the combined state of all compatible open PRs.