fix(graphic): add missing opacity option for graphic element style.

Author: plainheart

en/option/partial/zr-graphic.md

@@ -1591,7 +1591,11 @@ Y offset of shadow.
 
 ###${prefix} shadowColor(number) = undefined
 
-color of shadow.
+Color of shadow.
+
+###${prefix} opacity(number) = 1
+
+Opacity of this element.
 
 {{ use: partial-graphic-cpt-sub-prop-transition(
     prefix = ${prefix},

zh/option/partial/zr-graphic.md

@@ -1575,6 +1575,10 @@ Position of `textContent`.
 
 阴影颜色。
 
+###${prefix} opacity(number) = 1
+
+不透明度。
+
 {{ use: partial-graphic-cpt-sub-prop-transition(
     prefix = ${prefix},
     hostProp = 'style',