added line-stroke participant param

src/participant.typ

@@ -22,6 +22,11 @@
   invisible: false,
   shape: "participant",
   color: DEFAULT-COLOR,
+  line-stroke: (
+    dash: "dashed",
+    paint: gray.darken(40%),
+    thickness: .5pt
+  ),
   custom-image: none,
   show-bottom: true,
   show-top: true,
@@ -37,6 +42,7 @@
     invisible: invisible,
     shape: shape,
     color: color,
+    line-stroke: line-stroke,
     custom-image: custom-image,
     show-bottom: show-bottom,
     show-top: show-top

src/renderer.typ

@@ -432,11 +432,7 @@
             draw.line(
               (x, last-y),
               (x, line.at(1)),
-              stroke: (
-                dash: "dashed",
-                paint: gray.darken(40%),
-                thickness: .5pt
-              )
+              stroke: p.line-stroke
             )
           }
           lines.push(line)
@@ -462,11 +458,7 @@
           draw.line(
             (x, last-y),
             (x, line.at(1)),
-            stroke: (
-              dash: "dashed",
-              paint: gray.darken(40%),
-              thickness: .5pt
-            )
+            stroke: p.line-stroke
           )
           last-y = line.at(1)
         } else if event == "delay-end" {
@@ -486,11 +478,7 @@
       draw.line(
         (x, last-y),
         (x, y),
-        stroke: (
-          dash: "dashed",
-          paint: gray.darken(40%),
-          thickness: .5pt
-        )
+        stroke: p.line-stroke
       )
 
       // Draw lifeline rectangles (reverse for bottom to top)