* Update pl.js

I just added some translations

* Update pl.js

cf: https://github.com/ElemeFE/element/pull/9053

Add a comment to explain why year must be empty, because we definitely will not remember that!
(I am the one who filled it the last time :/)

In french, like in english, we don't say "Année" after the year number.

* fix: Replace cdn

* fix: Correct cdn host

* isue#9027 picker emit only real user change

* issue#9027 date-picker emit change if user real change only

* issue#9027 date-picker emit change if user real change only

see: https://github.com/ElemeFE/element/issues/8989

increase page-component-up z-index

根据英文文档，以及上下文描述，修正文档内容

$--table-header-background is defined but never used