docs: fix common chart option labelLayout

Author: xuefei1313

docs/assets/option/en/common/chart-spec.md

@@ -87,3 +87,7 @@ color: ['#BBD6B8', '#EA5455', '#19A7CE'],
     prefix = '#' + ${prefix},
     includeId = false
 ) }}
+
+#${prefix} labelLayout(string)='series'
+
+By default, it is laid out separately by series, and can be set to 'series' or 'region'. When set to `region`, the label of different series in the same region will be calculated together to prevent overlap.

docs/assets/option/zh/common/chart-spec.md

@@ -87,3 +87,7 @@ color: ['#BBD6B8', '#EA5455', '#19A7CE'],
     prefix = '#' + ${prefix},
     includeId = false
 ) }}
+
+#${prefix} labelLayout(string)='series'
+
+标签布局方式。默认按照系列单独布局，可设置为'series' 或 'region'。当设置为 region 时，相同 region 的系列标签会共同进行防重叠计算。