[Doc] Fix broken visitor badge link

[ZXJC-niusile]

Description

The visitor badge image in README.md was failing to load (returning a 410 error) because the upstream service glitch.me is down.
This PR replaces the broken link with the working alternative visitor-badge.laobi.icu to restore the badge functionality.

Checklist

Please feel free to remove inapplicable items for your PR.

• The PR title starts with [$CATEGORY] (such as [NN], [Model], [Doc], [Feature])
• Changes are complete (i.e. I finished coding on this PR)
• All changes have test coverage
• Code is well-documented
• To the best of my knowledge, examples are either not affected by this change, or have been fixed to be compatible with this change
• Related issue is referred in this PR

Changes

• Replaced defunct visitor-badge.glitch.me link with visitor-badge.laobi.icu in README.md.