docs: translate unit.md to chinese (#80)

---
name: Contribute to Newcar
about: Have a contribution to Newcar! Thank you!
---

**Description:** docs: translate unit.md to chinese

**Related Issues:** [List the issue numbers related to this PR]

**TODO**

**Checklist:**

- [ ]  Code has been reviewed
- [ ] Code complies with the project's code standards and best practices
- [ ]  Code has passed all tests
- [ ]  Code does not affect the normal use of existing features
- [x]  Documentation has been updated

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docs/content/zh/basic/unit.md

@@ -0,0 +1,15 @@
+---
+title: 单位制
+---
+
+# 单位制
+
+Newcar 提供了三种单位制：`frame`、`s` 和 `ms`。默认单位通常是秒，与应用程序绑定，除了 [Recorder](./recorder) 使用毫秒。
+
+## 设置单位制
+
+```ts
+app.config.unit = 'frame'
+app.config.unit = 's'
+app.config.unit = 'ms'
+```