Sync the config from the osu-wiki

[andy840119]

https://github.com/ppy/osu-wiki/blob/master/package.json
Guess it's OK to copy the config in here?

[andy840119]

what is .markdownlint.json:
https://ithelp.ithome.com.tw/articles/10280737

rules
https://github.com/DavidAnson/markdownlint/blob/main/doc/Rules.md