fix($cli): inferUserDocsDirectory ignore all node_modules

[cuijing1031]

Ignore node_modules in multi-layer catalogue in inferUserDocsDirectory

Summary

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• Bugfix
• Feature
• Code style update
• Refactor
• Docs
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• No

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Other information:
inferUserDocsDirectory There is a pattern to ignore node_modules for globby in inferUserDocsDirectory function in vuepress/lib/handleUnknowCommand.js. But if there is a folder which has node_modules, it don't work. ' !/node_modules/' will work for this case. There is a demo for this case: https://github.com/cuijing1031/globby-demo.git

[meteorlxy]

LGTM