feat(submodules): Add the nix recipes (bao-nix) repository

Signed-off-by: Miguel Silva <miguelafsilva5@gmail.com>

Author: miguelafsilva5

.gitmodules

@@ -3,4 +3,7 @@
 	url = git@github.com:bao-project/bao-ci.git
 [submodule "tests/bao-tests"]
 	path = tests/bao-tests
-	url = git@github.com/bao-project/bao-tests.git
+	url = git@github.com/bao-project/bao-tests.git	
+[submodule "tests/bao-nix"]
+	path = tests/bao-nix
+	url = git@github.com:bao-project/bao-nix.git