implemented aligned notes

src/note.typ

@@ -15,6 +15,16 @@
 )
 
 #let _note(side, content, pos: none, color: COL-NOTE, shape: "default", aligned: false) = {
+  if side == "over" {
+    if pos == none {
+      panic("Pos cannot be none with side 'over'")
+    }
+  }
+  if aligned {
+    if side != "over" {
+      panic("Aligned notes can only be over a participant (got side '" + side + "')")
+    }
+  }
   return ((
     type: "note",
     side: side,
@@ -22,7 +32,8 @@
     pos: pos,
     color: color,
     shape: shape,
-    aligned: aligned
+    aligned: aligned,
+    aligned-with: none
   ),)
 }
 
@@ -66,7 +77,7 @@
   if note.side == "over" {
     if type(note.pos) == array {
       let xs = note.pos.map(par => x-pos.at(pars-i.at(par)))
-      return xs.sum() / xs.len()
+      return (calc.min(..xs) + calc.max(..xs)) / 2
     }
   }
   return x-pos.at(pars-i.at(note.pos))
@@ -162,7 +173,7 @@
     anchor: "center"
   )
 
-  if note.pos != none or note.side == "across" {
+  if note.aligned-with == none and (note.pos != none or note.side == "across") {
     y -= h
   }