Merge pull request #5802 from jbriales/patch-2

Update sequenceDiagram.md

Author: sidharthv96

docs/syntax/sequenceDiagram.md

@@ -155,6 +155,9 @@ end
 box rgb(33,66,99)
 ... actors ...
 end
+box rgba(33,66,99,0.5)
+... actors ...
+end
 ```
 
 > **Note**

packages/mermaid/src/docs/syntax/sequenceDiagram.md

@@ -105,6 +105,9 @@ end
 box rgb(33,66,99)
 ... actors ...
 end
+box rgba(33,66,99,0.5)
+... actors ...
+end
 ```
 
 ```note