Add the SPA code as a submodule

Signed-off-by: Danila Fedorin <danila.fedorin@gmail.com>

.gitmodules

@@ -13,3 +13,6 @@
 [submodule "code/compiler"]
 	path = code/compiler
 	url = https://dev.danilafe.com/DanilaFe/bloglang.git
+[submodule "code/agda-spa"]
+	path = code/agda-spa
+	url = https://dev.danilafe.com/DanilaFe/agda-spa.git

config-gen.toml

@@ -1,5 +1,8 @@
 [params]
   [params.submoduleLinks]
+    [params.submoduleLinks.agdaspa]
+      url = "https://dev.danilafe.com/DanilaFe/agda-spa/src/commit/f0da9a902005b24db4e03a89c2862493735467c4"
+      path = "agda-spa"
     [params.submoduleLinks.aoc2020]
       url = "https://dev.danilafe.com/Advent-of-Code/AdventOfCode-2020/src/commit/7a8503c3fe1aa7e624e4d8672aa9b56d24b4ba82"
       path = "aoc-2020"