fix missing bracket in config.md

[Sciroccogti]

Related ISSUE

Input follow ISSUE URL address

Type Of Change

• [ ] 🐞 Bug fix (non-breaking change which fixes an issue)
• [ ] ✨ New feature (non-breaking change which adds functionality)
• [x] 📝 Document (This change requires a documentation update)
• [ ] 🎨 Theme style (Theme style beautification)
• [ ] ⚠ Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] 🔨 Workflow (Workflow changes)

Clear Describe

A clear and concise description of what update for target.

• docs: fix missing bracket in config.md

Description

Please enter detailed relevant motivation, background and implementation ... descriptive information.

Test Case

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test case.

[vercel[bot]]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

Name	Status	Preview	Updated
v2-vuepress-theme-gungnir	✅ Ready (Inspect)	Visit Preview	May 18, 2022 at 3:18AM (UTC)
vuepress-theme-gungnir	❌ Failed (Inspect)		May 18, 2022 at 3:18AM (UTC)

[Renovamen]

Thanks!