Update Chinese (Simplified) translations for version 2.1.0rc1 (#5849)

* i18n: (zh-CN) Add missing translations for multiple PRs.
Related PRs: #5838 #5762 #5835 #5837 #5832 #5823 #5814 #5757

* i18n: (zh-CN) Fix translation for #5823 / #5835

* i18n: (zh-CN) Improve translations

* i18n: (zh-CN) Improve translations

* i18n: (zh-CN) Change `发送者` to `作者`

* i18n: (zh-CN) Add missing translations for #5862

* i18n: (zh-CN) Add missing translation for #5874

* i18n: (zh-CN) Improve translations for keyboard shortcuts