[Tracking] Change the CDN from unpkg to jsDelivr

This is a tracking issue
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Change all the CDN link from `unpkg` to `jsDelivr`

From/for

- [x] docs (#1022)
- [x] https://github.com/docsifyjs/docsify-cli/tree/master/lib/template (https://github.com/docsifyjs/docsify-cli/commit/e8794309927a5a78f30f88aceab25d2c0014e0c1, https://github.com/docsifyjs/docsify-cli/commit/6545115098223be46ac44cb31a79b366179d7368)
- [x] plugins
- [x] Themes
