Add Chinese localisation for tiles of admonitions.

[mmcky]

Context

Currently admonitions are written automatically in English.

Proposal

We should update the extension to allow for Chinese titles (and other languages).

In this case Theorem should be 定理

English	Chinese
Definition	定义
Theorem	定理
Assumption	假设
Proof	证明

Tasks and updates

• [ ] enable localisation support in extension
• [ ] add Chinese for all admonition types.
• [ ] enable configuration setting for zh-cn