added test for sync edge cases

tests/sequence/sync/test.typ

@@ -35,3 +35,13 @@
     _seq("b", "b")
   })
 })
+
+#pagebreak()
+
+#diagram({
+  _sync({
+    _seq("a", "b", comment: [Abcdefgh])
+    _seq("b", "c", comment: [Foo\ bar], slant: 10)
+    _seq("c", "c", slant: 20)
+  })
+})