chore: add 2.5.1 changelog

docs: keep 2.4.11 docs && new sub folder for 2.5+

chore: update 2.5.0 changelog

chore: fix export issue generate by webpack upgrading

Table: fixed show-summary issue when multilevel header has fixed attr…

Tree: fix a bug that caused `showCheckbox` props on `Tree` can not affect their children `tree-node`

Radio: refine style

* Chore: upgrade webpack@4

* Chore: upgrade to webpack@4

* Chore: add babel-preset-stage-2

* Chore: fix test case

* Chore: upgrade webpack@4

* Docs: update docs

* Docs: update docs

* Chore: fix coveralls

* Chore: update yarn.lock

* Update i18n.md

Submit the internationalization profile of element in Kyrgyz

* Add international language - Kyrgyz

* Tag: add tag click event handle

* Tag: add doc and unit test.

* remove sponsor duotai

* recover douhui

i18n: add missing Catalan translations

Document: Fix a document difference

Checkbox: refine style

chore: use shadow CDN and fix typo

When the selected week spans across two years (e.g. 2018-12-30 2019-01-05),
they should be highlighted in both month tables.