docker workflow: support submodules initialisation (#155)

## Description

This ensures that the docker.yml action runs on repos that rely on git
submodule.

## Changes Made

We enable setting the checkout `submodules` by introducing an action
input `submodules`.
This was tested successfully on a private repository. 

## Checklist

- [x] I have used a PR title that is descriptive enough for a release
note.
- [x] I have tested these changes locally.
- [ ] I have added appropriate tests or updated existing tests.
- [ ] I have tested these changes on a cluster [name of the cluster] /
customer [name of the customer]
- [ ] I have added appropriate documentation or updated existing
documentation.

---------

Signed-off-by: Guillaume Tauzin <4648633+gtauzin@users.noreply.github.com>
Co-authored-by: Federico M. Facca <chicco785@users.noreply.github.com>

.github/workflows/docker.yaml

@@ -55,7 +55,12 @@ on:
         type: string
         default: ''
         description: Use caching mechanism for a given language
-
+      submodules:
+        required: false
+        type: boolean
+        default: false
+        description: True to initialize git submodules
+
 # Permissions needed
 # permissions:
 #   contents: read
@@ -79,6 +84,8 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v4
+        with:
+          submodules: ${{ inputs.submodules }}
       - name: Run pre-build
         run: |
           if test -f "Makefile"; then