implemented create event + create offset

gallery/notes.typ

@@ -136,3 +136,10 @@
   _seq("[", "a", comment: [Test])
   _note("left", [This is also a note])
 })*/
+
+#pagebreak()
+
+#chronos.diagram({
+  _seq("Bob", "Alice", comment: [Hello])
+  _evt("Other", "create")
+})

src/diagram.typ

@@ -123,6 +123,16 @@
         elmt: elmt,
         i: i
       )
+    } else if elmt.type == "evt" {
+      let par = elmt.participant
+      if not participant._exists(participants, par) {
+        let p = _par(par, from-start: elmt.event != "create").first()
+        participants.push(p)
+      
+      } else if elmt.event == "create" {
+        let i = participants.position(p => p.name == par)
+        participants.at(i).from-start = false
+      }
     }
   }
   linked = linked.dedup()

src/renderer.typ

@@ -279,6 +279,7 @@
         line.lines.push(("enable", y, elmt.lifeline-style))
       
       } else if elmt.event == "create" {
+        y -= CREATE-OFFSET
         shapes += participant.render(x-pos, par, y: y)
         line.lines.push(("create", y))
       }