GitLab

* Start writing BERT-Japanese doc

* Fix typo, Update toctree

* Modify model file to use comment for document, Add examples

* Clean bert_japanese by make style

* Apply suggestions from code review
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

* Split a big code block into two

* Apply suggestions from code review
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

* Add prefix >>> to all lines in code blocks

* Clean bert_japanese by make fixup
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>