docs: add echo and liquid tags Chinese translation (#549)

* docs: add echo and liquid tags chinese translation

* Update docs/source/zh-cn/tags/echo.md

Co-authored-by: Jun Yang <harttleharttle@gmail.com>

* Update docs/source/zh-cn/tags/echo.md

Co-authored-by: Jun Yang <harttleharttle@gmail.com>

* Update docs/source/zh-cn/tags/echo.md

Co-authored-by: Jun Yang <harttleharttle@gmail.com>

* Update Liquid.md

* Update Liquid.md

Co-authored-by: Jun Yang <harttleharttle@gmail.com>

Author: zxx457

docs/source/zh-cn/tags/echo.md

@@ -0,0 +1,20 @@
+---
+title: Echo
+---
+
+{% since %}v9.31.0{% endsince %}
+
+根据表达式输出渲染 HTML。和使用 `{{` expression `}}` 包裹模板效果一样，不同的是 echo 可以在 liquid 标签中使用，同时也支持过滤器。
+
+## echo
+
+输入
+```liquid
+{% assign username = 'Bob' %}
+{% echo username | append: ", welcome to LiquidJS!" | capitalize %}
+```
+
+输出
+```text
+Bob, welcome to LiquidJS!
+```

docs/source/zh-cn/tags/liquid.md

@@ -0,0 +1,28 @@
+---
+title: Liquid
+---
+
+{% since %}v9.31.0{% endsince %}
+
+通过 liquid 标签可以在一个分隔符中使用多个标签, 使 Liquid 逻辑书写更简洁。
+
+## liquid
+
+输入
+```liquid
+{% liquid
+  assign names = 'Bob, Sally' | split: ', '
+
+  for name in names
+    echo 'Hello, ' | append: name
+    unless forloop.last
+      echo ', '
+    endunless
+  endfor
+%}
+```
+
+输出
+```text
+Hello, Bob, Hello Sally
+```