Febs

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- [feature] 添加 febs.utils.sleep

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- [feature] 添加 febs.net 支持 fetch, jsonp
- [feature] 添加 requestAnimationFrame / cancelAnimationFrame

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- [feature] 添加 febs.file.dirExplorer
- [feature] 添加 febs.file.dirExplorerFilesRecursive
- [feature] 添加 febs.file.dirExplorerDirsRecursive

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- [feature] 添加global.__debug

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- [bugfix] febs.crypt.crc32

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- add bigint supported.
- add febs.controls in front.