Add language support - Korean

[amarantha-k]

Integrate the translation of the site done by Catalyze Research, which is currently hosted at https://catalyze-research.gitbook.io/xrpl-docs-korean/.

Note: With the recent updates to the content on xrpl.org, the translated content will need to be updated before it can be integrated.

This request also emphasizes the need for robust guidelines to ensure that translated versions remain in sync with the English version.