Update tutorial-discretisation.md

Author: ocots

docs/src/tutorial-discretisation.md

@@ -1,4 +1,4 @@
-# Discretisation methods
+# [Discretisation methods](@id tutorial-discretisation-methods)
 
 ## Discretisation formulas
 When calling `solve`, the option `disc_method=...` can be used to set the discretisation scheme.
@@ -95,4 +95,4 @@ Note that `time_grid` will override `grid_size` if both are present.
 ```@example main
 sol = solve(ocp, time_grid=[0, 0.1, 0.5, 0.9, 1], display=false)
 println(time_grid(sol))
-```
+```