Update remappings.txt for upgradeable contracts and set up submodule (#4639)

Co-authored-by: Hadrien Croubois <hadrien.croubois@gmail.com>
Co-authored-by: Ernesto García <ernestognw@gmail.com>
(cherry picked from commit abba0d047a)

.github/workflows/upgradeable.yml

@@ -29,4 +29,6 @@ jobs:
       - run: bash scripts/git-user-config.sh
       - name: Transpile to upgradeable
         run: bash scripts/upgradeable/transpile-onto.sh ${{ github.ref_name }} origin/${{ github.ref_name }}
+        env:
+          SUBMODULE_REMOTE: https://github.com/${{ github.repository }}.git
       - run: git push origin ${{ github.ref_name }}