docs: 添加pattern精选案例

[Angelii]

PR includes

• fixed #0
• add / modify test cases
• documents, demos

Screenshot

Before	After
❌	✅

[github-actions]

🎊 PR Preview bcfc272 has been successfully built and deployed to https://antvis-G2Plot-preview-pr-2818.surge.sh?type=diff&date=2021-08-24

🕐 Build time: 117.063s

_{🤖 By surge-preview}

[coveralls]

Pull Request Test Coverage Report for Build 1162884425

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.02%) to 95.605%

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Files with Coverage Reduction	New Missed Lines	%
src/utils/transform/word-cloud.ts	1	97.75%

Totals
Change from base Build 1160905716:	-0.02%
Covered Lines:	6491
Relevant Lines:	6611

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💛 - Coveralls