fix(markLine): symbolOffset incorrectly marked as mandatory
diff --git a/src/component/marker/MarkLineModel.ts b/src/component/marker/MarkLineModel.ts
index 4fed8c5..0c27667 100644
--- a/src/component/marker/MarkLineModel.ts
+++ b/src/component/marker/MarkLineModel.ts
@@ -61,7 +61,7 @@
     symbol?: string[] | string
     symbolSize?: number[] | number
     symbolRotate?: number[] | number
-    symbolOffset: number | string | (number | string)[]
+    symbolOffset?: number | string | (number | string)[]
 }
 
 // 2D markLine on any direction