build: add SII as dependency

Author: AayushSabharwal

Project.toml

@@ -21,6 +21,7 @@ Reexport = "189a3867-3050-52da-a836-e630ba90ab69"
 SciMLBase = "0bca4576-84f4-4d90-8ffe-ffa030f20462"
 SimpleNonlinearSolve = "727e6d20-b764-4bd8-a329-72de5adea6c7"
 SimpleUnPack = "ce78b400-467f-4804-87d8-8f486da07d0a"
+SymbolicIndexingInterface = "2efcf032-c050-4f8e-a9bb-153293bab1f5"
 
 [compat]
 ArrayInterface = "7"
@@ -37,4 +38,5 @@ Reexport = "0.2, 1.0"
 SciMLBase = "2.59.2"
 SimpleNonlinearSolve = "0.1, 1, 2"
 SimpleUnPack = "1"
+SymbolicIndexingInterface = "0.3.36"
 julia = "1.9"

src/DelayDiffEq.jl

@@ -13,6 +13,7 @@ using SimpleUnPack
 
 import ArrayInterface
 import SimpleNonlinearSolve
+import SymbolicIndexingInterface as SII
 
 using DiffEqBase: AbstractDDEAlgorithm, AbstractDDEIntegrator, AbstractODEIntegrator,
                   DEIntegrator, AbstractDDEProblem