docs: fix invalid contributing step

[lijinke666]

👀 PR includes

✨ Feature

• New feature

🎨 Enhance

• Code style optimization
• Refactoring
• Change the UI
• Improve the performance
• Type optimization

🐛 Bugfix

• Solve the issue and close #0

🔧 Chore

• Test case
• Docs / demos update
• CI / workflow
• Release version
• Other ()

📝 Description

1. 修改错误的贡献指南步骤, 应该是大写的 S2
   
2. 优化部分文档细节

🔗 Related issue link

🔍 Self Check before Merge

• Add or update relevant Docs.
• Add or update relevant Demos.
• Add or update relevant TypeScript definitions.

[github-actions]

🎊 PR Preview has been successfully built and deployed to https://s2-preview-pr-829.surge.sh

[github-actions]

Size Change: 0 B

Total Size: 184 kB

ℹ️ View Unchanged

Filename	Size
./packages/s2-core/dist/index.min.js	112 kB
./packages/s2-core/dist/style.min.css	356 B
./packages/s2-react/dist/index.min.js	67.9 kB
./packages/s2-react/dist/style.min.css	3.1 kB

_{compressed-size-action}

[codecov]

Codecov Report

Merging #829 (e03f5d2) into master (c4413c9) will increase coverage by 0.08%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #829      +/-   ##
==========================================
+ Coverage   70.86%   70.94%   +0.08%     
==========================================
  Files         166      166              
  Lines       11541    11541              
  Branches     2702     2702              
==========================================
+ Hits         8178     8188      +10     
+ Misses       2216     2212       -4     
+ Partials     1147     1141       -6     

Impacted Files	Coverage Δ
packages/s2-core/src/facet/base-facet.ts	68.83% <0.00%> (+2.03%)	⬆️

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[github-actions]

🎉 This PR is included in version @antv/s2-v1.1.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[github-actions]

🎉 This PR is included in version @antv/s2-v1.0.0-beta.17 🎉

The release is available on:

• npm package (@beta dist-tag)
• GitHub release

Your semantic-release bot 📦🚀