* [WIP] Refactor-docs-structure

* [Docs] Check link and fix rst  (#498)

* check link

* fix rst

* Fix conf.py

* Fix lint

* minor refine

* minor refine

* modify zh_readme and index.rst

* add migration exampls get_started design to en

* add tutorials to en

* correct chinese doc link

* Apply suggestions from code review

* Update docs/en/advanced_tutorials/distributed.md

Co-authored-by: Zaida Zhou <58739961+zhouzaida@users.noreply.github.com>

Co-authored-by: Mashiro <57566630+HAOCHENYE@users.noreply.github.com>

* [Fix] fix the typo

* [Fix] add the missing argument

* [Doc] Update runner documents.

* update

* fix link

* update

* update

* Update import manner of Runner

Co-authored-by: Wenwei Zhang <40779233+ZwwWayne@users.noreply.github.com>

* Modify val_interval and val_begin to be the attributes of TrainLoop.

* update doc

* fix lint

* type hint

* Replace markdownlint with mdformat to avoid installing ruby

* fix circleci

* [Doc] Refine runner doc.

* resolve comments

* [Doc] Add runner tutorial.

* update

* add advanced doc

* refine and add flow chart

* update

* update